Nuclear engineer Meena Mutyala argues that nuclear power is an environmentally ______________ technology, operating with essentially no emissions.

Choice D is the best answer. One definition of “benign” is “having no significant effect: harmless,” which is consistent with how “benign” is used in the sentence to refer to a technology that operates “with essentially no emissions.” Choices A, B, and C are incorrect because it makes no sense in context to refer to a technology that operates “with essentially no emissions” as “lavish” (abundant, profuse, excessive), “culpable” (deserving blame), or “antagonistic” (showing dislike or opposition).