Explanations:1. Answer: (A)
We learn from the passage that Alvarez had been using scaglia rosa as part of his studies on Earth’s polarity. Had he not have been, he would not have encountered the foraminifera, which led to his theory on dinosaur extinction. This supports answer (A).
(B) is tempting, but nowhere in the passage does it mention that the only way to learn about shifts in Earth’s magnetic fields is through the use of scaglia rosa.
(C) is similar to (B) in that we do not have enough information. That is nowhere in the passage does it say scientists have no other uses for scaglia rosa.
(D) Had Alvarez not noted the gap in the foraminfera, he would not have arrived at a theory on dinosaur extinction. Thus he would not have had any use for iridium.
(E) Had Alvarez not been studying Earth’s polarity, he would not have studied scaglia rosa and thus not noticed the gap in foraminfera.
2. Answer: (D)
The uniformitarian view is “any apparent extinctions” were a gap in the fossil record. This matches up best with (D).
(A) is wrong because a gap is not the same thing as tiny forams.
(B) is the opposite of what they would think
(C) is incorrect since uniformitarian view does not relate to iridium
(E) is incorrect because the uniformitarian view relates to fossil record
3. Answer: (A)
The passage says, “how long…iridium…answer this question.” This best supports (A).
(B) is wrong because iridium does not cause extinctions. (C) is incorrect because the forma, not the iridium, form in clay deposits. (D) is wrong because iridium does not relate to magnetic fields. (E) is incorrect because the passage suggests that iridium provides accurate, not inaccurate, conclusions about chronology.
4. Answer: (B)
Based on the startling amount of iridium that the Alvarezes found they concluded that only a meteorite could have caused the extinction of the dinosaurs. This matches up best with (B).
(A) is wrong because dinosaurs were not effected by the iridium itself but by the meteorite.
(C), while mentioned in the passage, does not answer the question.
(D) is wrong because the scaglia rosa showed a gap in foraminifera, not iridium.
(E) is incorrect because the passage does not mention the scientific community, nor does it imply that the Alvarez’s explanation was a default one.
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