Sentence Correction

Recently documented examples of neurogenesis, the production of new brain cells, include the brain growing in mice when placed in a stimulating environment or neurons increasing in canaries that learn new songs.

(A) the brain growing in mice when placed in a stimulating environment or neurons increasing in canaries that

(B) mice whose brains grow when they are placed in a stimulating environment or canaries whose neurons increase when they

(C) mice's brains that grow when they are placed in a stimulating environment or canaries' neurons that increase when they

(D) the brain growth in mice when placed in a stimulating environment or the increase in canaries' neurons when they

(E) brain growth in mice that are placed in a stimulating environment or an increase in neurons in canaries that

This is very much a meaning question.

Ask yourself what was placed in the stimulating environment?

A) It wasn't the brain growing as the sentence implies (in mice is a preposition)
B) The pronoun 'they' implies the brains were placed
C) Same as B
D) Here it is the brain growth
E) Finally, with the use of the relative pronoun 'that' it is clear that the mice were placed in the environment.