Rat Kiley and Curt Lemon were throwing a smoke grenade back and forth. When Curt Lemon drops it and steps on the grenade, it blows up and eventually dies. The technology of the grenade caused it to blow up when he stepped on it.
MAN vs. NATURE
O'Brien is heartbroken after he kills a man. He feels very guilty that he had taken a life away from a man. O'Brien's thinks about the life this man did and would have had however, he killed him and he can't help but feel very shameful and guilty.
After passing out in the dentist office getting his teeth checked, Curt Lemon felt like everyone thought he wasn't brave. Therefore that night, Curt Lemon went back to the dentist and insisted that they pull out his perfectly good tooth to prove his bravery.
MAN vs. SELF
After Rat Kiley's best friend Curt Lemon died, he got frustrated and kept shooting and eventually killed a baby water buffalo to get his anger out. Rat Kiley used this helpless baby water buffalo to make him feel better about is best friend dying.
Norman Bowker found it very difficult to readjust and fit in after coming back from the war. He can't keep his job and he drops out of junior college. Bowker can't fit back in to his previous life and no one seemed to care so eventually gave up and hung himself.