Correct Answer: Silent

Solution : The correct choice will be the first option.

The most appropriate antonym for the word vociferous is silent.

Vociferous: This term describes someone or something loud, outspoken, or vocal, often intensely or vehemently.

Silent: The antonym of vociferous , silent refers to the absence of sound, noise, or speech. A silent person does not speak loudly or vehemently.

The meanings of the other options are:

Sullen: This term refers to a gloomy or morose disposition, and it is not directly opposite in meaning to vociferous.

Gallant: Gallant refers to someone brave, noble, or chivalrous, and it is not an antonym of vociferous.

Pugnacious: Pugnacious describes someone eager or quick to argue, quarrel, or fight, and it is not an antonym of vociferous.