the study’s claims that the time span between the asteroid hitting earth and the extinction of
the dinosaurs was shorter than had been previously thought. Thus, (B) is correct. The data,
not the techniques, was used to propose a new theory. Similarly, the author doesn’t mention
the techniques in order to prove the conclusion correct. The author wants to make sure that
people understand that the data was better than before, so (A) and (C) are not correct.
Choice (D) can be mistaken for meaning that the new data counters the old assumption, but
the purpose of mentioning the device is to lend authority to the claim.
C The word preclude is used to describe what would happen to a causal relationship between
the asteroid and the dinosaur extinction if the previous data was correct. The scientist who
uses the word explains that the previous data showed the extinction to have occurred before
the asteroid hit, and that would completely undermine any claims that the asteroid had
caused the extinction. Therefore, preclude must means something like “prevent from
happening.” Choice (B) is close to this meaning, but (C) is the correct answer because to
bar means to stop something completely, rather than just limit it. Choice (A) does not make
sense; no matter what the older data showed, the data could not cause a relationship
between the asteroid and the extinction; it could only confirm or disprove hypotheses about
the relationship. Choice (D) means “to strike with light blows” and does not make sense in
the context of the sentence.
D The author of Passage 2 mentions tektites because they represent residue from the asteroid,
while volcanic ash provides information about the timing of the large-scale volcanoes that
erupted. The aging of these samples affected the theories that were set forth. Thus, (D) is
correct. The tektites don’t suggest another cause, (A); they definitely don’t diminish the role
of the asteroid in the demise of the dinosaurs, (B); and they don’t substantiate that the
volcanoes caused the most damage, (C), since that’s too vague and unsupported by the
passage.
C Think about the evidence from the passage that helped you answer the previous question:
Tektites were mentioned because they helped prove that there was not a causal relationship
between the impact and the extinction. Only (C) works, and it’s the correct answer.
C The correct answer is (C), as Passage 1 mentions mammals and their rise to dominance and
Passage 2 does not. Both passages described the size of the asteroid, so (A) is incorrect.
Both passages say that the primary cause of the extinction was an asteroid that hit before the
extinction took place, so (B) is incorrect. Both passages indicate that previous theories
have been reconsidered and adjusted in light of an evaluation of evidence, so (D) is
incorrect.
B The main difference between the passages is that Passage 2 puts forth the idea that the
ecosystems were already in decline when the asteroid hit, while Passage 1 doesn’t mention
that possibility when it discusses the volcanoes. Otherwise, both passages ultimately
ascribe the KT extinction to the asteroid. Thus, (B) is correct. Choice (A) is incorrect
because the asteroid didn’t cause the volcanic eruptions. Choice (C) is incorrect because
Passage 2 clarifies the timing of the impact and states that past estimates were inaccurate.
Passage 2 doesn’t discuss mammals at all, so (D) is incorrect.