15. Recently documented examples of neurogenesis（神经形成）, 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
key:E 为什么D不对呢? | 
