Big Book Reading Comprehension Page 540

GRE Verbal Problem Solving
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I chose (A) but the correct answer is (D).

Can someone explain how (A) is wrong?

Nowhere does the passage say that FM echoes alert the bat the bag to moving targets. In fact, the same is clearly metioned for the CF echoes in line 16.

Thanks,
Vaibhav

2

It might be helpful to go through process of elimination for each answer here.

B) the passage doesn’t talk about a range of targets but it does talk about a spectrum of echoes. Ets trying to trick us.

C)FM reports the targets direction in space and CF reports the targets presence so both do this. So this is out.

D)the last sentence states this exact thing

E)CF echoes report only the targets presence not the size and shape so this is out

A)the first paragraph talks about the process of transmission and reflection that alerts the bat to the target and that both FM and CF are part of this process. This choice says only CF does so this is out.

This was tricky! I’m not fully sure of my logic so would love to hear your thoughts on this.

3

I get your explanation for (A) but the keyword here is ‘moving’. (A) talks about moving targets.

Moving targets are explained only when talking about CF in line 16 ‘its motion relative to the bat’s’.
That’s why I was willing to go with (A).

Now, I can almost hear Greg say, ‘Cool! What’s your reason to eliminate (D)?’

Well, the question talks about the difference between CF echoes and FM echoes, and (D) talks about CF echoes that concerns only a section of bat species.

4

This is such a tough question. I reworded all the sentences and then summarized the main ideas of each paragraph. Then looked at it again in the context of the question. The question is basically asking how CF differs from FM?

So let’s list what we know about them.

  • FM is wide, CF is narrow.
  • FM sends characteristics about the target (including direction in space or the way the target is facing) and CF sends ONLY the targets location.
  • FM and CF are changed during the process of echolocation
  • FM and CF help bats see stuff about the target.

Why D is right? In some species, CF echoes enable some species to judge whether it’s closing in on its target. Lines 17-19 say this exact thing.

Why is A wrong? Only CF echoes alert the bat to moving targets. Well we know from the fourth bullet above that both FM and CF helps the bat see stuff about the target. CF ONLY shows the location, but FM shows the way it looks, feels, AND its direction in space, meaning the way it’s traveling.

So the difference isn’t that CF only shows where the moving target is. They both do this. The difference is that only CF allow the bat to make changes in the moment to adjust its location relative to the target when hunting.

Again, check me here. But I’m hoping this is closer.

5

That makes sense.

Thanks for the effort you put into this :slight_smile:

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