Neanderthals had a vocal tract that resembled those of the a

[ghong14]

Whales had a tail that resembled those of the dolphin, a characteristic that contributes to their mastery of the waters.

(A) Whales had a tail that resembled those of the dolphin.
(B) whales had a tail resembling an dolphin’s
(C) The tail of whales resembled an dolphin’s
(D) The whale's tail resembled the dolphins’
(E) The tails of the whales resembled those of the dolphins

This is a question from the official guide that I modified. I think the question here is that there is a parallelism issue. However, the correct answer is actually B. I don't see how that could be parallel.

I thought E had the best parallelism. (E) The tails of the whales resembled those of the dolphins

For B (B) whales had a tail resembling an dolphin’s arent parallel.

[RonPurewal]

ok, i know the problem that inspired this.

as far as (e) goes, you've killed the part that actually makes it incorrect.
if you wrote (e) as
The tails of the whales resembled those of the dolphins and so could swim with agility and grace,...
... then you'd have an illogical sentence suggesting that the tails themselves could swim.
this is also the problem with the original choice (e); the subject doesn't make sense with the second verb. go back and check it out.

as for as choice (b) is concerned, remember that it's pointless to question or doubt the official answers. if you disagree with one of GMAC's correct answers ... well, they win, and you lose.

in this construction, "a dolphin's" is "a dolphin's [tail]", which is ok because the word "tail" has already appeared.
it's like saying "My wife is taller than yours" -- you don't have to say "wife" again.