A Study of Salivary Testosterone Levels Found That Early-Evening Testosterone

A study of salivary testosterone levels found that early-evening testosterone levels did not differ on nights when men subsequently had sex compared to nights when they did not; late-evening testosterone levels, however, were higher on "sex" nights (after sex had occurred) compared to "no sex" nights. The authors of this study concluded that

A) all men are interested in sex regardless of testosterone levels.
B) testosterone causes sexual desire.
C) sexual desire is highest in late evening compared to early evening.
D) testosterone plays a role in sperm production but not in sexual activity.
E) sexual activity stimulates testosterone release.