TOEFL Reading 1

*wobble: to shake or move from side to side
*tilt: to be in a sloping position 

1. The word "prevaied" in the passage is closest in meaning to  ruled existed  survived  triumphed

   Geologists have shown that for about 80 percent of the past 2.5 million years, ice-age conditions have prevailed on the Earth's surface. During the past one million years, increased glacial conditions have run in cycles of approximately 100,000 years.

   
   

   2. What can be inferred from paragraph 2 about the factors that contribute to glaciation?  They affect the Earth's spin. They are geologically recent. Оnly three factors relate to levels of sunlight. Other factors than those relating to the sunlight affect ice buildup. Paragraph 2 is marked with an arrow [->].

   -> Many different factors may contribute to these increases in glaciation at regular intervals throughout Earth's more geologically recent history. The three most prominent factors probably relate to the amount of sunlight that reaches the Earth. This varies over time for three main reasons. First, the planet wobbles as it spins, due to the pull of the sun and moon. Furthermore, the Earth tilts on its axis and the degree of tilt changes over time. Finally, the orbit of the Earth around the sun is elliptical and the length of the major axis of the ellipse changes over a period of about 100,000 years. A mathematician named Milutin Milankovitch discovered in the 1930s that the pattern of insolation, or sunlight, predicted by these eccentricities in the Earth's movement matched the period of the last several eras of intense glaciation.

   
   

   3. The phrase "these eccentricities" in the passage refers to all of the following EXCEPT  the various movements of the Earth as it spins  the degree of change in the Earth's tilt over time  the pattern of insolation matching the Earth's movement  the changing distance to the sun during the Earth's elliptical orbit

   Many different factors may contribute to these increases in glaciation at regular intervals throughout Earth's more geologically recent history. The three most prominent factors probably relate to the amount of sunlight that reaches the Earth. This varies over time for three main reasons. First, the planet wobbles as it spins, due to the pull of the sun and moon. Furthermore, the Earth tilts on its axis and the degree of tilt changes over time. Finally, the orbit of the Earth around the sun is elliptical and the length of the major axis of the ellipse changes over a period of about 100,000 years. A mathematician named Milutin Milankovitch discovered in the 1930s that the pattern of insolation, or sunlight, predicted bythese eccentricities in the Earth's movement matched the period of the last several eras of intense glaciation.

   
   

   4. Scientists accepted the Milankovitch theory even though  the peaks of sunlight occurred at intervals of 95.000 and 125.000 years  the peaks of insolation and intense glaciation did not match  there were climate records of a 400,000-year cycle there were microfossil deposits on the sea floor

   [Refer to the full passage]

   
   

   5. In paragraph 4, why does the author suggest the image of a flat plane?  To help the reader visualize the positions and movements of the heavenly bodies To demonstrate to the reader how the Earth orbits the sun  To support the argument that the orbital inclination increases tilting  To show how the Milankovitch theory doesn't explain the cyclical changes in climate Paragraph 4 is marked with an arrow ->.

   -> These and other problems with the Milankovitch cycles led some researchers to seek alternative explanations for the cyclic arrival of extended ice ages. In the 1990s, it was discovered that the orbital inclination of the Earth to the sun and planets could also be responsible for climate changes. If we imagine a flat plane with the sun in the center and the planets revolving around it, the Earth slowly moves in and out of the flat plane by a few degrees, repeating the cycle every 100,000 years. Two scientists. Muller and MacDonald, have proposed that it is this orbital inclination which is ultimately responsible for the periods of glaciation and warming. They argue that because of the oscillation. the Earth periodically travels through clouds of debris, in the form of dust and meteoroids. Such debris could reduce the amount of solar energy reaching the surface of our planet, thus plunging it into regular cold periods.

   
   

   6. The word "it" in the passage refers to  such debris  solar energy  the surface  our planet

   These and other problems with the Milankovitch cycles led some researchers to seek alternative explanations for the cyclic arrival of extended ice ages. In the 1990s, it was discovered that the orbital inclination of the Earth to the sun and planets could also be responsible for climate changes. If we imagine a flat plane with the sun in the center and the planets revolving around it, the Earth slowly moves in and out of the flat plane by a few degrees, repeating the cycle every 100,000 years. Two scientists. Muller and MacDonald, have proposed that it is this orbital inclination which is ultimately responsible for the periods of glaciation and warming. They argue that because of the oscillation, the Earth periodically travels through clouds of debris, in the form of dust and meteoroids. Such debris could reduce the amount of solar energy reaching the surface of our planet. thus plunging it into regular cold periods.

   
   

   7. In paragraph 4, the author explains that  Milankovitch did not know about the orbital inclination of the Earth glaciation occurs when the orbital inclination has entered a new cycle the Earth always travels through clouds of debris after moving out of the plane by a few degrees the amount of solar energy reaching the Earth's surface causes the changes of temperature Paragraph 4 is marked with an arrow [->].

   -> These and other problems with the Milankovitch cycles led some researchers to seek alternative explanations for the cyclic arrival of extended ice ages. In the 1990s, it was discovered that the orbital inclination of the Earth to the sun and planets could also be responsible for climate changes. If we imagine a flat plane with the sun in the center and the planets revolving around it, the Earth slowly moves in and out of the flat plane by a few degrees, repeating the cycle every 100,000 years. Two scientists. Muller and MacDonald, have proposed that it is this orbital inclination which is ultimately responsible for the periods of glaciation and warming. They argue that because of the oscillation, the Earth periodically travels through clouds of debris, in the form of dust and meteoroids. Such debris could reduce the amount of solar energy reaching the surface of our planet. thus plunging it into regular cold periods.

   
   

   8. What problem in the Milankovitch theory was mentioned as being explained by the Muller and MacDonald theory?  The climate records obtained by studying microfossil deposits not matching his predicted cycle The irregularities of the Earth's movements through orbital inclinations not following any pattern The Earth's spin wobbling in relation to the Earth's oscillating inclination The peak in the ice ages occurring at intervals between 95,000 and 125,000 years instead of 400,000

   [Refer to the full passage.]

   
   

   9. The word "persuaded" in the passage is closest in meaning to  convinced discouraged affected challenged

   However, many researchers in this field are not yetpersuaded by the inclination hypothesis. The main problem is that the amount of dust that falls to the ground when the Earth travels through space debris is relatively small -not enough to produce radical climate changes. Volcanic eruptions, for example, release much greater amounts of ash and dust and have relatively little effect on climate. Supporters have countered that the by-products created by the dust as it vaporizes on entering the atmosphere cause subtle changes to the energy levels. Nevertheless, the necessary physical proof has yet to be found to convince the skeptics.

   
   

   10. What problem is associated with the Muller and MacDonald theory?  The amount of debris that is released from volcanoes is proportional to the amount of interstellar dust. The amount of ash from volcanoes and space dust that vaporizes in the atmosphere is itoo small.  The amount of dust entering the atmosphere is less than the amount of ash and dust released by volcanoes. The by-products created by vaporized space dust cause relevant changes to the energy levels.

   [Refer to the full passage.]

   
   

   11. Look at the four squares [?] that indicate where the following sentence could be added to the passage.  When the Earth is at its furthest from the sun, less sunlight reaches the surface. Where would the sentence best fit? Choose the letter of the square that shows where the sentence should be added.  A  B  C  D

   Many different factors may contribute to these increases in glaciation at regular intervals throughout Earth's more geologically recent history. [A] The three most prominent factors probably relate to the amount of sunlight that reaches the Earth. This varies over time for three main reasons. First. the planet wobbles as it spins, due to the pull of the sun and moon. [B] Furthermore, the Earth tilts on its axis and the degree of tilt changes over time. [C] Finally, the orbit of the Earth around the sun is elliptical and the length of the major axis of the ellipse changes over a period of about 100,000 years. [D] A mathematician named Milutin Milankovitch discovered in the 1930s that the pattern of insolation, or sunlight, predicted by these eccentricities in the Earth's movement matched the period of the last several eras of intense glaciation.

   
   

   12. Directions: Select the appropriate phrases from the answer choices and match them to the flaws in the ice-age theories to which they relate. TWO of the answer choices will NOT be used. This question is worth 4 points. Write the letters of the answer choices in the spaces where they belong.  Refer to the full passage.

   Answer Choices A) Data of climate records not coinciding with predicted intervals of sunlight B) Temperature rises occurring before the increase of sunlight C) The irregularities of the Earth's movement during its orbit around the sun D) The inconsistency between the periods of sunlight and glaciation E) The relatively mild effect of volcanic eruptions on the climate F} The orbital inclination of Earth through clouds of debris G) The relatively small amount of interstellar debris reaching Earth H) The lack of clear support from ocean sediment data I) The lack of physical evidence in support of the effects of the inclination hypothesis

   Flaws in the Milankovitch Cycles Theory *  *  *  *  Flaws in the Muller and MacDonald Theory *  *  *

   
   Questions 13-26

*topographic: relating to the natural features of land 
*olfactory: connected with the sense of smell

1. In paragraph 1, it is understood that some birds don't migrate south in the winter because they  already live in warmer conditions live in areas that have an abundant food supply  have difficulty surviving the frigid temperatures  are suited to the difficult conditions Paragraph 1 is marked with an arrow [->].

   -> The phenomenon of seasonal bird migration has been known about for thousands of years, but it is still not fully understood by scientists. Not all birds migrate, but generally speaking the more northerly the breeding ground, the more likely is it that a species will migrate south for the winter. The main reason for this annual shifting of residence is that during the northern winters food becomes scarce and the cold temperatures make survival difficult. Some species are well adapted to these harsh conditions, but for those that aren't, moving south to warmer conditions is advantageous.

   
   

   14. The word "those" in the passage refers to  northern winters cold temperatures harsh conditions some bird species

   The phenomenon of seasonal bird migration has been known about for thousands of years, but it is still not fully understood by scientists. Not all birds migrate, but generally speaking the more northerly the breeding ground, the more likely is it that a species will migrate south for the winter. The main reason for this annual shifting of residence is that during the northern winters food becomes scarce and the cold temperatures make survival difficult. Some species are well adapted to these harsh conditions, but for those that aren't, moving south to warmer conditions is advantageous.

   
   

   15. According to paragraph 2, what are the results of changes in the weather?  The change in the length of the day The secretion of hormones by the birds The expenditure of calories  The onset of migration Paragraph 2 is marked with an arrow [->].

   -> Changes in the weather can trigger the start of the journey south, although birds in the Northern Hemisphere seem to know when it is time to migrate south before the winter. In some species at least, the changes in the length of the day cause glands in the birds' bodies to secrete hormones that produce other changes, which ready the birds for the long flight south. At this time fat starts to accumulate under the skin, and this provides a store of energy for the long flight when they will be expending more calories flying than they can obtain during their brief rest stops.

   
   

   16. The word "accumulate'' in the passage is closest in meaning to  build up fill in  break up cut back

   Changes in the weather can trigger the start of the journey south, although birds in the Northern Hemisphere seem to know when it is time to migrate south before the winter. In some species at least, the changes in the length of the day cause glands in the birds' bodies to secrete hormones that produce other changes, which ready the birds for the long flight south. At this time fat starts to accumulate under the skin, and this provides a store of energy for the long flight when they will be expending more calories flying than they can obtain during their brief rest stops.

   
   

   17. All of the bird migration patterns are mentioned in the passage EXCEPT  the migration north from the Southern Hemisphere the migration east or west toward milder climates  the migration from mountainous regions to lower altitudes the migration from east to west towards hotter climates.

   [Refer to the full passage.]

   
   

   18. The word "precisely" in the passage is closest in meaning to  finally exactly entirely decisively

   Perhaps the most mysterious and as yet not totally understood aspect of bird migration is how birds can navigate such long distances and arrive so precisely at their destination. Various possibilities exist. The most obvious explanation is that they learn the topographic features of their route. However, it is not feasible that this method could be used for crossing larger stretches of water or very long trips across whole continents. Another possible explanation is that some birds may use magnetic fields. Scientists have actually detected tiny crystals of magnetite in the olfactory tract of some species, and homing pigeons have been shown to follow magnetic field lines of the Earth.

   
   

   19. It can be inferred that polarization patterns  absorb sunlight are tied in the center are invisible at night  cause a magnetic force

   [Refer to the full passage.]

   
   

   20. Why does the author mention Haidinger's brush?  To understand the phenomenon To describe the pattern To explain what birds see To define the fuzzy ends

   [Refer to the full passage.]

   
   

   21. The word "subjected" in the passage is closest in meaning to  exposed subjugated  constrained invited

   Scientists believe that some birds navigate by use of star positions; this has been established with at least one species. In a series of studies, caged birds were subjectedto the projection of the nighttime Northern Hemisphere inside a planetarium. All stars rotate around Polaris, the pole star, and this movement seemed to give the birds the information they needed to orientate themselves in the correct direction. However, some recent research contradicts this. Perhaps it is not the lack of movement of the pole star but rather the constellation patterns that guide them. It has also been found that when fewer stars were visible on the planetarium ceiling, the birds' sense of direction became poorer. And this, too, implies that the general star pattern does have some bearing on orientation.

   
   

   22. According to paragraph 6, how do some birds navigate during the night?  By using a projection of the star positions By circling around the pole star By orientating themselves using the constellations  By getting their bearings from a few visible stars Paragraph 6 is marked with an arrow [->].

   -> Scientists believe that some birds navigate by use of star positions; this has been established with at least one species. In a series of studies, caged birds were subjected to the projection of the nighttime Northern Hemisphere inside a planetarium. All stars rotate around Polaris, the pole star, and this movement seemed to give the birds the information they needed to orientate themselves in the correct direction. However, some recent research contradicts this. Perhaps it is not the lack of movement of the pole star but rather the constellation patterns that guide them. It has also been found that when fewer stars were visible on the planetarium ceiling, the birds' sense of direction became poorer. And this, too, implies that the general star pattern does have some bearing on orientation.

   
   

   23. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.  Birds needing to orientate themselves in the right direction seemed to use the information they get from the stars that rotate around Polaris. The pole star seemed to be used by birds to get the information they needed because they were able to orientate themselves using the star's rotation in the correct direction. Birds needing to correct the Polaris direction in which to orientate themselves seemed to use the fact that all stars rotate. The stars rotating in the correct direction around the pole star is what seemed to give the birds the information they needed for orientating themselves to Polaris.

   Scientists believe that some birds navigate by use of star positions; this has been established with at least one species. In a series of studies, caged birds were subjected to the projection of the nighttime Northern Hemisphere inside a planetarium. All stars rotate around Polaris, the pole star. and this movement seemed to give the birds the information they needed to orientate themselves in the correct direction. However, some recent research contradicts this. Perhaps it is not the lack of movement of the pole star but rather the constellation patterns that guide them. It has also been found that when fewer stars were visible on the planetarium ceiling, the birds' sense of direction became poorer. And this, too, implies that the general star pattern does have some bearing on orientation.

   
   

   24. The word "this" in the passage refers to   The number of stars that were visible The relative loss of the birds' sense of direction The constellation patterns that guide birds The pole star's stationary position

   Scientists believe that some birds navigate by use of star positions; this has been established with at least one species. In a series of studies, caged birds were subjected to the projection of the nighttime Northern Hemisphere inside a planetarium. All stars rotate around Polaris, the pole star. and this movement seemed to give the birds the information they needed to orientate themselves in the correct direction. However, some recent research contradicts this. Perhaps it is not the lack of movement of the pole star but rather the constellation patterns that guide them. It has also been found that when fewer stars were visible on the planetarium ceiling, the birds' sense of direction became poorer. Andthis, too, implies that the general star pattern does have some bearing on orientation.

   
   

   25. Look at the four squares [?] that indicate where the following sentence could be added to the passage.  Over short distances the birds could recognize particular landscapes such as river valleys and shapes of hills. Where would the sentence best fit? Choose the letter of the square that shows where the sentence should be added.  A  B  C  D

   Perhaps the most mysterious and as yet not totally understood aspect of bird migration is how birds can navigate such long distances and arrive so precisely at their destination. Various possibilities exist. [A] The most obvious explanation is that they learn the topographic features of their route. [B] However, it is not feasible that this method could be used for crossing larger stretches of water or very long trips across whole continents. [C] Another possible explanation is that some birds may use magnetic fields. [D]Scientists have actually detected tiny crystals of magnetite in the olfactory tract of some species, and homing pigeons have been shown to follow magnetic field lines of the Earth.

   
   

   26. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. Write the tetters of the answer choices in the spaces where they belong. Refer to the full passage. Scientists have proposed several methods that birds use for orientating themselves during their seasonal migrations. *  *  *  Answer Choices A) Birds not only migrate north or south depending on which hemisphere they live in, but they also migrate along coastal regions or in and out of mountainous areas. B) Birds' ability to detect gradations of polarization patterns in sunlight could give them a way for determining directions. C) Changes in both the weather and the length of day can cause the birds' bodies to make physical changes to prepare them for the long flights. D) The principal reason for birds to migrate is that most bird species are not adapted to the harsh winter conditions and the scarcity of food during that season. E) The star patterns and the way the stars rotate around the fixed position of the pole star could give birds the direction in which to navigate. F) Birds may use their knowledge of the features of the landscape, although this seems unlikely given the distances that birds migrate.

   
   Questions 27-39

*negligible: too small to be important 
*picocurie: a level of radiation activity

1. The phrase "this element" in the passage refers to  lead radon uranium polonium

   Radon is a radioactive gas that is invisible and odorless. It forms during the decay of uranium-238, and in decaying. itself produces solid heavy metal radioactive particles of polonium, lead, and bismuth. The parent element, uranium, is distributed in rocks and soils in many regions of the world, although usually in negligible amounts. However, concentrations of this element occur in certain rocks, and under certain conditions it is dissolved by underground water and carried over great distances before seeping into other rocks and soils.

   
   

   28. The word "seeping" in the passage is closest in meaning to  leaking spilling releasing erupting

   Radon is a radioactive gas that is invisible and odorless. It forms during the decay of uranium-238, and in decaying, itself produces solid heavy metal radioactive particles of polonium, lead, and bismuth. The parent element, uranium, is distributed in rocks and soils in many regions of the world, although usually in negligible amounts. However, concentrations of this element occur in certain rocks, and under certain conditions it is dissolved by underground water and carried over great distances before seeping into other rocks and soils.

   
   

   29. In paragraph 2, what can be inferred about the relationship of radon and health problems?  The gas has to have time to decay in order to cause health problems.  Since radon is chemically inert, it cannot lead to health problems. As a gas, radon disperses in the wind and consequently isn't a health problem. The gas has to disintegrate before it can seep into buildings. Paragraph 2 is marked with an arrow [->].

   -> Since radon is a gas, it can move from the ground into the air, where it is dispersed by the winds. If it infiltrates buildings, however, it can build up over time and lead to serious health problems. In fact, the radon itself is chemically inert and so does not enter into chemical reactions with other substances. It is readily dissolved in blood and circulates through the body until it is expelled, usually before it has had time to decay. The health problems associated with radon activity arise from the radioactive products of its disintegration, mentioned above.

   
   

   30. The word "disintegration" in the passage is closest in meaning to  breakdown collapse corrosion  failure

   Since radon is a gas, it can move from the ground into the air, where it is dispersed by the winds. If it infiltrates buildings, however, it can build up over time and lead to serious health problems. In fact, the radon itself is chemically inert and so does not enter into chemical reactions with other substances. It is readily dissolved in blood and circulates through the body until it is expelled, usually before it has had time to decay. The health problems associated with radon activity arise from the radioactive products of its disintegration, mentioned above.

   
   

   31. Health problems associated with radon are caused by  radioactive uranium certain heavy metals decaying gases some chemical reactions

   [Refer to the full passage.]

   
   

   32. Which of the sentences below best expresses the essential information in the highlighted sentence? Incorrect choices change the meaning in important ways or leave out essential information.  Unlike the radon, which is scattered without danger, its products accumulate as the radon disintegrates. Like the radon itself, the decay products are scattered safely and accumulate as the radon decays. Like the decaying radon, the progeny are dispersed in accumulations, which can cause harm. Unlike the dispersed radon, which accumulates safely, the products of decay are dangerous.

   The products of the decay process, especially polonium-218 and polonium-214, emit radiation, which kills or damages living cells, causing genetic mutations and cancer. These radon progeny are not dispersed harmlessly like radon itself but accumulate as the radon decays. Outside the body, these solid materials can attach themselves to dust particles and surfaces throughout a building and then be inhaled. The decay products can also stick to tobacco leaves during growth and then enter the body when the tobacco is smoked. Inside the body these dangerous by-products of radon become lodged in lung tissue and the bronchial tubes. As these decay, they emit alpha and beta particles and gamma rays. Of these, the alpha particles can do the most damage since they are the bulkiest of the three and therefore cannot penetrate very far into living tissue. Because of this relative immobility. concentrations of the particle form and damage cells in the immediate area. Beta particles and gamma rays are less dangerous since they travel further and are less concentrated in the tissues.

   
   

   33. According to paragraph 3, some products of decay cause damage because they  emit gamma rays cannot penetrate living tissue very deeply are highly mobile  seep into houses and form concentrations of radiation Paragraph 3 is marked with an arrow [->].

   -> The products of the decay process, especially polonium-218 and polonium-214, emit radiation, which kills or damages living cells, causing genetic mutations and cancer. These radon progeny are not dispersed harmlessly like radon itself but accumulate as the radon decays. Outside the body, these solid materials can attach themselves to dust particles and surfaces throughout a building and then be inhaled. The decay products can also stick to tobacco leaves during growth and then enter the body when the tobacco is smoked. Inside the body these dangerous by-products of radon become lodged in lung tissue and the bronchial tubes. As these decay, they emit alpha and beta particles and gamma rays. Of these, the alpha particles can do the most damage since they are the bulkiest of the three and therefore cannot penetrate very far into living tissue. Because of this relative immobility, concentrations of the particle form and damage cells in the immediate area. Beta particles and gamma rays are less dangerous since they travel further and are less concentrated in the tissues.

   
   

   34. The phrase "uranium daughter" in the passage refers to  water radon particles air

   The primary way that radon penetrates buildings is through foundations. It enters through cracks in basement floors, drains, loose-fitting pipes, and exposed soil areas. Radon also finds its way into water, although if the water is exposed to the atmosphere or agitated, the radon disperses into the air. Because of this, concentrations of this uranium daughter are not high in rivers, but water drawn from underground sources into homes can have elevated levels.

   
   

   35. According to the passage, all of the following are true about radon EXCEPT  it is invisible it cannot be detected it cannot be smelled it is radioactive

   [Refer to the full passage.]

   
   

   36. It can be understood from paragraph 6 that  reducing the amount of radon in your home is pointless because of the amount of radon outside even though it is possible to test buildings for radon accumulation, it is not possible to minimize the level of radiation activity the use of concrete sealing and active ventilation systems can reduce the amount of radon to an acceptable level using concrete sealing and installing active ventilation systems reduces the amount of usable living space Paragraph 6 is marked with an arrow [->].

   ->It is now possible to have buildings tested for radon accumulation. In an average home, this is about 1.3 picocuries per liter, which is considered an acceptable although not a totally safe level. If these levels are above 4 picocuries per liter of air, then homeowners are advised to reduce the amount seeping into the living space. This can be achieved through various means including concrete sealing and the installation of active ventilation systems. It is not possible to completely eradicate traces of radon since the natural outdoors level averages 0.4 picocuries per liter, but minimizing the amount is a prudent preventative measure.

   
   

   37. The word "prudent" in the passage is closest in meaning to  sensible necessary practical realistic

   It is now possible to have buildings tested for radon accumulation. In an average home, this is about 1.3 picocuries per liter, which is considered an acceptable although not a totally safe level. If these levels are above 4 picocuries per liter of air, then homeowners are advised to reduce the amount seeping into the living space. This can be achieved through various means including concrete sealing and the installation of active ventilation systems. It is not possible to completely eradicate traces of radon since the natural outdoors level averages 0.4 picocuries per liter, but minimizing the amount is a prudent preventative measure.

   
   

   38. Look at the four squares [?] that indicate where the following sentence could be added to the passage.  But this research has been criticized for being based on too few subjects. Where would the sentence best fit? Choose the letter of the square that shows where the sentence should be added.  A  B  C  D

   The chief health risk from inhaling radon or its daughter products is lung cancer. [A] Scientists have concluded that exposure to this carcinogen is the second leading cause of this disease in the United States. [B] Major scientific organizations believe it contributes to approximately 12 percent of the incidence in the United States alone. It is true that some research has cast doubt on the likelihood of residential radon accumulations contributing to cancer rates.[C] Other larger scale studies contradict the neutral findings. For example, a recent study of 68.000 underground miners who were exposed to high levels of radon shows that they are five times more likely to die of lung cancer than the general population. [D] Smokers, whose incidence of lung cancer is significantly higher than the nonsmoking population, are even more at risk if they are exposed to high levels of radon.

   
   
   

   39. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. Write the letters of the answer choices in the spaces where they belong.  Refer to the full passage. Radon can seep into a building, where its decay products can lead to health problems. *  *  *  Answer Choices A) Although radon can enter a building in many different ways, it also escapes through cracks in the foundations. B) Concentrations of the radon by-products attach themselves to particles in the air inside buildings and are breathed into the lungs. C) People who smoke or work in mines are at greater risks of getting lung cancer that is related to alpha particles than those who work in buildings. D) The by-product alpha particles are too heavy to disperse through the tissues, so they accumulate in the lungs where they kill or damage lung cells. E) Radon does not cause lung cancer because it is chemically inert and therefore readily dissolves in the blood, where it eventually is expelled from the body. F) Preventative measures can be taken to reduce the amount of exposure to radon in living spaces, but it is not possible to completely eliminate the gas from the atmosphere.