Having a History of Psychological Problems Before Going into Combat

Having a history of psychological problems before going into combat

A) will make a soldier much more likely to develop PTSD.
B) will make a soldier much more likely to develop PTSD only if the combat situation is extreme.
C) sometimes increases risk of PTSD, but may lower it because the person is used to anxiety and copes automatically with it.
D) doesn't have an impact on developing PTSD.