Testosterone and Estradiol Are Male and Female Sex Hormones, Respectively

Testosterone and estradiol are male and female sex hormones, respectively, in many vertebrates. In what way(s) do these molecules differ from each other? Testosterone and estradiol ________.

A) are structural isomers but have the same molecular formula
B) are cis-trans isomers but have the same molecular formula
C) have different functional groups attached to the same carbon skeleton
D) are enantiomers of the same organic molecule