Researchers Have Discovered a Possible Biological Basis for Sexual Orientation

Researchers have discovered a possible biological basis for sexual orientation that has become known as "the older brother effect," meaning ________.

A) as the number of older brothers a man has decreases, his chances of being gay increases
B) as the number of older brothers a woman has increases, so do her chances of being lesbian
C) as the number of older brothers a man has increases, so do his chances of being gay
D) the oldest brother is more likely to be gay