Researchers blamed the low rate of growth in the harbor's toad populat

Researchers blamed the low rate of growth in the harbor's toad population on lake toxicity as well as on the weather,
hotter and more humid than average in the Ohio region, which slowed metabolism and reproductive activity.

(A) hotter and more humid than average in the Ohio region, which slowed
(B) which was hotter and more humid than average in the Ohio region, slowing
(C) since it was hotter and more humid than average in the Ohio region, which slowed
(D) being hotter and more humid than averages in the Ohio region, which slowing
(E) having been hotter and more humid than was average in the Ohio region, and slowed

problem: modification error.

'Which' must immediately follow the noun it is modifing/describing. here, it is not the ohio region that is causing the slow metabolism but rather, it is the whether.

on that note, A C, and D, are out.

Also in d, 'being' not always correct on the gmat.
in E, 'having been' is not relevant here.

Correct answer is B