If You Were to Summarize the Main Results with Regard

If you were to summarize the main results with regard to the biological factors in the cause of PTSD from the study of twins who served in Vietnam, what would you say?

A) Genetic factors account for little in PTSD.
B) Level of exposure did not predict PTSD symptoms.
C) Genetic factors were most significant in accounting for arousal/anxiety symptoms.
D) Whether individuals were exposed to trauma was not affected by genetic influences.