Of the following, which is the least plausible hypothesis for why natural selection has not eliminated genes for male homosexuality?

a. Perhaps the relatives of a homosexual male have more than an average number of children.

b. Homosexual people might spread their genes by helping their brothers and sisters rear their children.

c. Maybe there is no gene for homosexuality. Instead, an environmental event produces an epigenetic effect that can be transmitted from one generation to the next.

d. Some homosexual men have children.