The claim that sums up the general meaning of "Chaming Billy" is that soldiers in the Vietnam War needed training in physical and psychological survival tactics, as shown in option D.
We can arrive at this answer because:
Paul receives good physical training, combat and survival tactics and although he is prepared, he is still very scared.
This shows that in addition to physical training, psychological training was needed to ensure that soldiers were more efficient and had balanced mental health.
More information on mental health at the link:
https://brainly.com/question/24698326