Because it is possible that neither L nor V volunteered. If L is out, then R, M, T and S are in, and F and V are out, resulting in the following complete list of volunteers: In: R M T S Out: L V F
Since the question requires us to find a pair of employees such that at least one of the members must volunteer, and we can come up with a scenario where both L & V are out, we can conclude that (C) is incorrect.
