Research Shows That People Who Have a Genetic Predisposition to Depression

Research shows that people who have a genetic predisposition to depression are more likely to display depressive episodes than people without the predisposition when they are not coping effectively with environmental stress in their lives. This is evidence that

A) a genetic predisposition to depression is the only cause of the disorder
B) environmental stress is the only cause of depression
C) genetic predispositions interact with environmental stress to cause depression
D) neither genetic predispositions nor environmental stress cause the disorder