Sentence Correction

Antarctica receives more solar radiation than does any other place on Earth, yet the temperatures are so cold and the ice cap is reflective, so that little polar ice melts during the summer; otherwise, the water levels of the oceans would rise 250 feet and engulf most of the world's great cities.

A. is reflective, so that little polar ice melts during the summer; otherwise,
B. is so reflective that little of the polar ice melts during the summer; were it to do so,
C. so reflective that little polar ice melts during the summer, or else
D. reflective, so that little of the polar ice melts during the summer, or
E. reflects so that little of the polar ice melts during the summer; if it did

Well, I haven't seen the question before, but it seems to me that (C) is the best answer.

It appears to be testing parallelism and idioms. We know that a common GMAT idiom is "so x that." For example, we might say, "John is so tall that he can touch the ceiling."

In this sentence we see "...the temperatures are so cold..." and we expect to find the word that to finish out the idiom. Answer choices (A), (D), and (E) offer us the phrase so that, which will not work.

Both choices (B) and (C) offer a parallel structure that is idiomatic. If you're not certain when deciding between two choices, it's usually best to pick the shorter one. This rule of thumb would lead you to C.

Why is C better than B? Well, it seems to be more efficient in its use of words. Little polar ice is better than little of the polar ice. The word it is suspicious looking. Does it refer to the ice or to the summer?

I'm not perfectly happy with C. I'd rather see the phrase "or else" replaced with the word "otherwise." Still, beggars can't be choosers. I'll stick with C.