Q10

[kitmitzi]

I had no idea how to answer this question. I ended up choosing B because in the introduction there wasn't evidence provided that LHB evidence was on Earth. The correct answer is D. I don't understand that at all. Scientist's motivation for studying LHB isn't mentioned anywhere in the article, so how can one deduce that this is why the author mentions it?

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[bbirdwell]

This one's kind of tricky. So the question is "why does the author say that the LHB should have struck the Earth?"

Well, the very next phrase in that sentence (line 9), says that this would have "profound consequences" for the history of Earth. This is to say, it's interesting. The rest of the passage is a discussion of how and when the LHB occurred.

So, to ballpark, the phrase in question is used as a launching point for the rest of the passage.

(B) is not the answer because we don't actually know that there is a lack of evidence on Earth. In fact, if anything, evidence from Earth is mentioned as the subject of the entire last paragraph.

They want you to choose (B) because the author has used a common idiomatic expression in an unexpected way. Typically when I say "I should have gone to the movies," it means I didn't. When speaking, we tend to use the word "should" to suggest that the event did not actually occur, but that's not how the author is using it here.

The author is saying, if the moon got hit, then the Earth should also have been hit... and this serves to lead toward a search for evidence and ideas to confirm that the Earth did get hit, rather than to suggest that it did not. Many times, people say "If X is true, we should expect to find Y...and in fact we do." Here, the author does something similar, in effect saying, "If X is true, we should find Y... here are some ideas about that."

It's subtle, and not particularly well written, which makes it tough.