Topic: Adjective (বিশেষণ),

Best Answer Explained in Below-:

The word "only" in the sentence "Piyahas slept only three hours" functions as an adverb. Adverbs modify verbs, adjectives, or other adverbs, providing additional information about the manner, degree, frequency, or limitation of the action or quality described.

In this context, "only" specifies the extent of the hours Piyahas slept. It indicates a limitation, suggesting that three hours is less than normal or expected, emphasizing that this is the sole amount of sleep he had. This limiting function is characteristic of adverbs, which often clarify or restrict the meaning of a verb—in this case, "slept."

If "only" were a noun, it would represent a person, place, thing, or idea, which it does not in this sentence. As an adjective, it would modify a noun, but here, it modifies the verb "slept." Finally, "only" is not a preposition, as prepositions connect nouns or pronouns to other words in a sentence. Therefore, the correct classification of "only" in this context is C) an adverb.