6. In paragraph 4, all the following questions are answered EXCEPT: A . Why is there a layer of clay between the rocks of the Cretaceous and Cenozoic? B. Why were scientists interested in determining how long it took to deposit the layer of clay at the end of the Cretaceous? C. What was the effect of the surprising observation scientists made? D. Why did scientists want more information about the dinosaur extinctions at the end of the Cretaceous? 7 . Paragraph 5 implies that a special explanation of the Ir in the boundary clay is needed because A . the Ir in microscopic meteorites reaching Earth during the Cretaceous period would have been incorporated into Earth’s core B. the Ir in the boundary clay was deposited much more than a million years ago C. the concentration of Ir in the boundary clay is higher than in microscopic meteorites D. the amount of Ir in the boundary clay is too great to have come from microscopic meteorites during the time the boundary clay was deposited
8. The word “disruption” in paragraph 6 is closest in meaning to A. exhaustion B. disturbance C. modification D. disappearance
9 . Look at the four letters that indicate where the following sentence could be added to the passage . Consequently, the idea that the Ir in the boundary clay came from microscopic meteorites cannot be accepted. Where would the sentence best fit? Ir has not been common at Earth’s surface since the very beginning of the planet’s history. Because it usually exists in a metallic state, it was preferentially incorporated in Earth’s core as the planet cooled and consolidated. Ir is found in high concentrations in some meteorites, in which the solar system’s original chemical composition is preserved. Even today, microscopic meteorites continually bombard Earth, falling on both land and sea. By measuring how many of these meteorites fall to Earth over a given period of time, scientists can estimate how long it might have taken to deposit the observed amount of Ir in the boundary clay . (A) These calculations suggest that a period of about one million years would have been required. (B) However, other reliable evidence suggests that the deposition of the boundary clay could not have taken one million years . (C) So the unusually high concentration of Ir seems to require a special explanation. (D)
A . Option A B. Option B C. Option C D. Option D
10 . 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 your answer choices after each of the three bullets . You can either write the letter of your answer choice or you can copy the sentence.
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