Which of the following is true concerning the effect of sex hormones?

a. Hormone injections can be used to easily manipulate sexual behavior in males but not in females.

b. Hormone injections can be used to easily manipulate sexual behavior in both males and females.

c. Sex hormones have a more direct effect on nonhuman animals than on humans.

d. The levels of sex hormones are more constant in females than in males.

e. While studies have shown that ovulation is associated with changes in women’s fantasies, they have not established an association between ovulation and women’s sexual behavior.