Which of the Following Factors Is Not an Example of a Gene

Which of the following factors is not an example of a gene by environment interaction:

A) a genetic predisposition for depression results in depressive symptoms only when the person experiences many life stressors
B) a strong genetic predisposition for alcoholism results in alcoholism only when the person decides to drink alcohol
C) a genetic predisposition to be emotionally reactive increases the positive effects of supportive caregiving and increases the negative effects of poor parenting
D) a, b, and c are all examples of gene by environment interactions