A Zoo Is Hand-Rearing an Endangered Species of Songbird

A zoo is hand-rearing an endangered species of songbird. What is the best approach to help prepare the males to attract mates?

A) Expose the males to a mentor male bird singing their species' song during the critical period.
B) Expose the males to female pheromones from their species, to initiate development of song circuits during the critical period.
C) Expose the males to each other during the critical period, to initiate development of song circuits during the critical period.
D) Expose the males to a variety of birdsongs during the critical period.