Which of the following findings supports the argument that homosexual men are the result of the ...

Which of the following findings supports the argument that homosexual men are the result of the maternal immunity hypothesis?
 
  a. Mothers, after having multiple male children, make antibodies against male-specific proteins, reducing their effects in subsequent males
  b. The testosterone levels in mothers increase after every male child, flooding the subsequent male's bodies with more and more hormones.
  c. Male homosexuals tend to have more younger brothers than male heterosexuals, indicating that their mother must have high testosterone levels in her uterus.
  d. Antibodies in the prenatal period result in the increase of androgens in the womb, causing affected individuals to become homosexual.