Unlike Morgenthau who defends the necessity of a unipolar system to better organize international structure and Raymond Aron who counts on a multipolar structure because of its homogeneity in terms of power; Waltz is the only great realist who is in favor of bipolarity (Battistella, 2012: 151). Mearsheimer, in his essay about future of the post-Cold War World, particularly Europe, emphasizes that a transition to a multipolar order from a bipolar one provokes instability. The correct answer is B.