Correct Answer:
Option D - In the given sentence 'why' is a relative adverb. A relative adverb is an adverb that introduces an adjective clause. Relative adverbs are 'when', where, why and how. Each one has its own role; 'where' is an adverb of place, 'when' is an adverb of time, 'why' is an adverb of reason.
D. In the given sentence 'why' is a relative adverb. A relative adverb is an adverb that introduces an adjective clause. Relative adverbs are 'when', where, why and how. Each one has its own role; 'where' is an adverb of place, 'when' is an adverb of time, 'why' is an adverb of reason.