The conventional view is that asteroids strike the earth at random locations, thereby randomly affecting various aspe...

Shiyi-Zhang on June 11, 2019

Why is D correct?

Why is D correct? Why are the other answers incorrect?

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shunhe on December 27, 2019

Hi @Shiyi-Zhang,

To begin with, we note that this is a strengthen question. As such, we need the answer choice that most bolsters the arguments made by the iconoclastic geophysicist. Her claim is that some kind of highly organized natural process has helped shape how asteroids have struck the earth. As evidence, she cites an unusual pattern of impact craters. A good answer would provide some kind of natural explanation for why these asteroids made this pattern. With that in mind, let's dive into the answer choices.

(A) is wrong because it doesn't talk about the causes of the asteroids striking in such a pattern, but instead talks about the effects of asteroid strikes, which is irrelevant to the specific issue that we are addressing.

(B) is wrong for the same reason as (A). It discusses the effects of asteroids hitting the same spots on earth, but it doesn't talk about the reasons why the asteroids might do that in the first place, which is what we need.

(C) is wrong because it actually weakens the geophysicist's argument. If it's a single cluster of meteors that struck the earth at the same time, it's actually more likely that they happened to form a halo-like swath across the northern Hemisphere than a bunch of isolated meteors spread across a long period of time.

(D) provides the answer we're looking for. (D) tells us that an innate property of the earth causes gravitational interactions with approaching asteroids that affect their orbits before impact. Asteroids that have similar orbits before impact will likely make patterns when they strike the earth, and so (D) gives us a reason for the pattern.

(E) is wrong because it, like (C), weakens the argument. If there were some kind of highly organized natural process affecting asteroid flight paths, then we might expected to have seen it affect other asteroids in the past. (E) tells us the opposite. It tells us that the halo-like swath is a unique occurrence, which increases the probability that is occurred randomly. Hope this helps!