Women Are Generally Less Vulnerable to Infections but More Vulnerable

Women are generally less vulnerable to infections but more vulnerable to auto-immune,or self-attacking,disease.Why?

A) Because women tend to have stronger immune systems than men.
B) Because women engage in more health-damaging behaviors than men.
C) Because estrogen and auto-immune diseases are highly correlated.
D) Because women have the genetic marker for auto-immune susceptibility.