Select the most appropriate ANTONYM of the highlighted word.
Regardless of their diversity, all flowers have a uniform function, the reproduction of the species through the production of seed.

Correct option is D

Diversity- the fact of many different types of things or people being included in something.
 The most appropriate antonym of "diversity" is "uniformity," which means sameness or consistency.
 Synonyms: Variety, differences, heterogeneity, multiplicity, divergence.
 Antonyms: Uniformity, sameness, homogeneity, conformity, similarity.
Meanings of the given words are:
 Melancholy: a feeling of sadness or depression.
 Equilibrium: a state of balance or stability.
 Affinity: a natural liking or attraction towards someone or something.