He found a can of a medicine that kills different types of bugs and parasites. Candy tells him the man who stayed in his bunk before was very clean and probably has a can as a precaution.
This is your answer for the parenthetical citation (World Magazine, 2009, page 56)
I would say B and D also. A and C make no sense and are irrelevant. Keep using deductive reasoning and have a good day!