Research investigating the causes of gender differences in behavior suggests that select one:
a. during infancy there are not gender differences between the toy preferences of boys and girls.
b. no gender differences have been found between the toy preferences of boy and girl monkeys.
c. females exposed to excessive levels of testosterone during birth tend to dislike rough-and-tumble play.
d. females exposed to excessive levels of testosterone during birth tend to enjoy rough-and-tumble play.