Some Explanations for the Persistence of a Heritable Tendency for Male

Some explanations for the persistence of a heritable tendency for male homosexuality are based on the idea that the relatives of gay men might have tended to have more surviving offspring than do the relatives of straight men.Which of the following specific explanations have been proposed?
1) Gay men tend to invest heavily in the well-being of their nieces and nephews
2) Gay men's nieces and nephews tend to have especially strong resistance to infectious disease
3) Gay men's mothers and aunts tend to have many children.

A) 1 only
B) 1 and 2 only
C) 1 and 3 only
D) 2 and 3 only
E) 1,2,and 3