Synonyms are words which have the same or nearly the same meaning in the same language.
Antonyms are words which have opposite meaning in comparison to the other.
Option D)strident is correct as the word strident means (of a sound) loud and harsh; grating and the word euphonious means (of sound, especially speech) pleasing to the ear.
Both the words are opposite of each other.
The other options are not correct as they do not have the opposite meaning to the given word.
Lethargic, literary, and musical means affected by lethargy; sluggish and apathetic, concerning the writing, study, or content of literature, especially of the kind valued for quality of form, and relating to musicrespectively.