A region of the canary forebrain shrinks during the nonbreeding season and enlarges when breeding season begins.This change is probably associated with the annual

A)addition of new syllables to a canary's song repertoire.
B)crystallization of subsong into adult songs.
C)sensitive period in which canary parents imprint on new offspring.
D)renewal of mating and nest-building behaviours.
E)elimination of the memorized template for songs sung the previous year.