A) testosterone.
B) dihydrotestosterone.
C) estradiol.
D) a and b
E) All of the above

A) sexual dimorphism in the brain is often due to sex-specific differences in programmed cell death.
B) sexual dimorphism is regulated by reception of circulating sex hormones.
C) sex determination is cell-autonomous, based on karyotype.
D) sex-specific survival of a muscle promotes survival of its motor neuron(s).
E) All of the above

A) No song at all
B) A species-specific rudimentary innate song similar to that of acoustically isolated birds
C) A rudimentary innate song distinct from that of acoustically isolated birds
D) A mature song that resembles that of his own species
E) A mature song that resembles that of the tutor's species