Why Are Men with Older Brothers,but Not Men with Older

Multiple Choice

Why are men with older brothers,but not men with older sisters or those who are only children,more likely to be gay?

A) Mothers are more likely to unknowingly treat their youngest sons like daughters.
B) A mother's heightened immune response with subsequent male-fetus pregnancies affects brain development.
C) Older brothers are likely to deride and belittle the youngest brother,creating a more sensitive,fearful,and confused individual.
D) Older brothers are more likely to protect and guard the youngest brother,shielding him from rough-and-tumble play and traditional masculine rituals.