Bunuel
Just as the ancient Celtic stories of Arthur had a relationship to Malory's Le Morte d’Arthur, then the Muslim tales of the Prophet's Mi'raj were to Dante's Divine Comedy.
(A) Just as the ancient Celtic stories of Arthur had a relationship to Malory's Le Morte d'Arthur, then the Muslim tales of the Prophet's Mi'raj were to
(B) The ancient Celtic stories of Arthur were to Malory's Le Morte d’Arthur what the Muslim tales of the Prophet's Mi'raj were to
(C) What the ancient Celtic stories of Arthur did for Malory's Le Morte d’Arthur, so the Muslim tales of the Prophet's Mi'raj were doing for
(D) How the ancient Celtic stories of Arthur related to Malory's Le Morte d’Arthur was exactly how the Muslim tales of the Prophet's Mi'raj were in relation to
(E) So as the ancient Celtic stories of Arthur had a relationship to Malory's Le Morte d’Arthur, just so the Muslim tales of the Prophet's Mi'raj had it to
Magoosh Official Explanation:
This is a tricky question, comparing one relationship to another relationship. I will go through the choices individually.
Choice (A) uses the idiomatically incorrect structure "Just as P, then Q". Furthermore, this choice purports to place in parallel "had a relationship to" to "were to", which does not work. This is incorrect.
Choice (B) uses the correct idiom for this situation: P is to Q as X is to Y. This is the idiom for comparing two relationships, and this choice follows this idiom perfectly.
Choice (C) uses a very informal, colloquial structure—"what P did for Q"—this would pass in American spoken English, but this is not an appropriate structure for the formal language of the GMAT. This is unacceptable.
Choice (D) is grammatically correct, and possibly logical correct, but very wordy and indirect. It uses the construction "how P related to Q was exactly how X was in relation to Y"—even if this does correctly communicate the idea, it is far too indirect and bloated. There is no way this would be correct on the GMAT.
Choice (E) uses the idiomatically incorrect structure "So as P, just so Q". Furthermore, the pronoun "it" does not have a clear, unambiguous antecedent. This one is incorrect.
The only possible answer is choice (B).