In Male White-Crowned Sparrows, the Sensitive Period for Song Learning

In male white-crowned sparrows, the sensitive period for song learning is:

A) when they must be exposed to any bird song, so they can practice singing the appropriate species-specific song as adults.
B) when they begin to practice their song, and they are producing an imperfect version of the adult male's song.
C) when they must hear adult male song if they are later to be able to sing a proper adult male song of their own.
D) when, if they are presented with a live tutor of a closely related species, they can learn the other species' song instead of their own.
E) when, if they are presented with tapes of their own species' song and the song of a closely related species, they can learn the songs of both species.