Hello Everyone!
Let's tackle this question, one thing at a time, and narrow it down to the correct choice! To begin, here is the original question with any major differences between the options highlighted in orange:
In the past several years, astronomers have detected more than 80 massive planets, most of them as large or larger than Jupiter, which circle other stars.
(A) most of them as large or larger than Jupiter, which circle
(B) most of them as large or larger than Jupiter and circling
(C) most of them at least as large as Jupiter, circling
(D) mostly at least as large as Jupiter, which circle
(E) mostly as large or larger than Jupiter, circling
After a quick glance over the options, there are a couple things we can focus on to narrow down our choices:
1. as large or larger than / at least as large as
2. which circle / and circling / circling / which circle / circling
Since #1 on our list will eliminate 2-3 options right away, let's start there! This is actually an issue with idiom structure. Any time you see the phrase "as large" in a sentence, it MUST be followed up with "as." It's not correct to say something is "as large than" something else. Otherwise, the meaning gets muddled or confusing. Here's an example:
The tree is at least as tall as the house. = CORRECT
The tree is as tall or taller than the house. = INCORRECT
The tree is as tall as or taller than the house. = CORRECT
So, let's see how our options stack up:
(A) most of them as large or larger than Jupiter, which circle
(B) most of them as large or larger than Jupiter and circling
(C) most of them at least as large as Jupiter, circling
(D) mostly at least as large as Jupiter, which circle
(E) mostly as large or larger than Jupiter, circling
We can eliminate options A, B, and E because they don't use the correct structure "as large as."
Now that we have it narrowed down to only 2 options, let's tackle #2 on our list: circling/which circle. To make problems easier to spot, let's add in the non-underlined portions:
(C) In the past several years, astronomers have detected more than 80 massive planets, most of them at least as large as Jupiter, circling other stars.
This is CORRECT! The -ing modifier here clearly refers back to the 80 massive planets that circle other stars.
(D) In the past several years, astronomers have detected more than 80 massive planets, mostly at least as large as Jupiter, which circle other stars.
This is INCORRECT because "which" modifiers always modify the noun directly before the comma. In this case, it's trying to modify Jupiter, which is not circling other stars - the 80 massive planets are!
There you have it - option C is the only one that uses the correct modifier and idiom structure "as large as."
Don't study for the GMAT. Train for it.
