Replace the underlined word in the following sentence with an antonym from the options given:

The mellifluous strains of the song floated into the hall, stirring the complacent emotions of many.

Option 1 -> euphonic means pleasant-sounding or harmonious, which is a synonym of mellifluous, not an antonym.

Option 2 -> mature means fully developed or ripe, which is unrelated to the quality of sound described by mellifluous.

Option 3 -> harsh means rough, grating, or unpleasant-sounding, which is the direct opposite of mellifluous (sweet-sounding, smooth).

Option 4 -> doleful means sad or mournful, which describes emotional tone but not the opposite of the smooth, pleasant sound quality of mellifluous.

Hence, Option 3: harsh -> Mellifluous means sweet-sounding and smooth like honey, while harsh means rough and grating, making them perfect antonyms in terms of sound quality -> correct