The answer is D. Calumniate.
To nurture is to care for and encourage the growth or development of something. To neglect is to fail to care for or pay attention to something. To denigrate is to speak about someone or something in a very negative way. To calumniate is to make false and damaging statements about someone.
In the original pair of words, “nurture” and “neglect,” the two words are opposites. Nurturing something means caring for it and helping it to grow, while neglecting something means failing to care for it and allowing it to decline. In the answer pair, “denigrate” and “calumniate,” the two words are also opposites. Denigrating someone means speaking about them in a very negative way, while calumniating someone means making false and damaging statements about them.
The other options do not have the same relationship as the original pair of words. To reveal something is to make it known or visible. To extol someone or something is to praise them highly. To recognize someone or something is to identify them or acknowledge their existence.