Sentence Correction

Many scientists say that attempts to remove a species of the black bee in India did not work because the pesticides that were utilized were effective only in eradicating the natural enemies of the black bee, which made it easier for them to grow and proliferate.

(A) which made it easier for them

(B) which makes it easier for it

(C) thus making it easier for them

(D) thus making it easier for the black bee

(E) thereby, it was made easier for the black bee

OA is D