This is a Logic question that asks you to weaken an argument. The author cites a problem: a pesticide that is effective in killing bedbugs is no longer available for use. Thus, the author claims, there is no effective means to kill the bedbugs in the United States. The problem here is that the author makes a very large jump between “replaced by weaker pesticides” and “there is no effective means.” Finding something that attacks this assumption would be a good way to weaken the argument. Regarding choice (A), the behaviors of bedbugs have nothing to do with the ability to eradicate them. Choice (B) does not specify how bedbugs were eradicated in other parts of the world. It is possible that all successful eradications elsewhere relied on DDT. Correct choice (C) opens up the possibility that there might be an approved means to eradicate the dreaded bedbug in the United States. It also calls the author’s conclusion about there being “no effective means for eradicating bedbugs in the United States” into question. Choice (D), though largely out of scope, might be viewed as strengthening the author’s conclusion, as it points to more evidence that existing pesticides are not effective on bedbugs. However, eliminating one possibility is not the same as eliminating all possibilities, which is what the author does in the conclusion. As for choice (E), the number of infestations has nothing to do with the ability to eliminate bedbugs in the United States.