Interestingly, it has been determined that aggressive behavior is not limited to the breeding season among nonmigratory (sedentary) populations of song sparrows, and that the behavior is regulated by

A) estradiol during the breeding season, but testosterone during the nonbreeding season.
B) high levels of testosterone during the breeding season, but low levels of testosterone during the nonbreeding season.
C) surprisingly low levels of testosterone during the breeding season, but higher levels of testosterone during the nonbreeding season.
D) testosterone during the breeding season, but estradiol during the nonbreeding season.