Thanks for the question! Let’s take a look at the question. We’re told that the policy of nuclear deterrence works. Why? Because major powers are scared of a nuclear world war, proven by the fact that a third world war between superpowers hasn’t happened. The question asks for a flaw in the argument. Taking a look at (D), it tells us that major powers have engaged in smaller-scale military operations since the end of WWII, while not engaging in nuclear warfare. (D) is of course true in the real world, which is why it might seem tempting, but we need to be careful about importing real-world knowledge into the LSAT. What we need to deal with here is strictly the argument that we’re presented with, and (D) isn’t a problem with the argument. (D) actually, in a way, strengthens the argument because it helps show that the major powers have been staying away from larger-scale military operations because those might devolve into the kind of nuclear world war that the author says that the major powers fear.
(E), on the other hand, states a flaw in the argument. (E) tells us that there might be other reasons for the lack of a third world war between superpowers that the author isn’t considering. Failing to consider and eliminate plausible alternate explanations can reasonably be a flaw in the argument, and so we pick (E).
Hope this helps! Feel free to ask any further questions that you might have.
