Which of the following is true about the genetic factors of depression?

A) First-degree relatives of people with depression are not likely to have depression themselves.
B) Twin studies of major depression find lower concordance rates for monozygotic twins than for dizygotic twins.
C) Abnormalities on the serotonin transporter gene could affect the stability of individuals' moods.
D) It has been proven that genetics plays a greater role in this disorder for women than for men.