An argument completion asks us what answer choice would be the best to slot in to the argument as a new conclusion.
However here the question actually gives us a potential conclusion, and asks us to think about what answers choice would be useful to consider when evaluating the new argument. This is an argument evaluation question, which is kind of a hybrid between a strengthen and a weaken where we need to find information that would address (either positively or negatively) a major uncertainty in the argument.
