The correct answer is 'Adverb'. Key Points - Here, in the given above sentence the underlined part "besides" is used as an adverb. - As per the general rule, an adverb is a word that modifies a verb, an adjective, another adverb, or even a whole sentence. - When used as an adverb, besides means 'in any case' or 'anyway'. - Example: - Tom would never survive life in the army; he's not tough enough. Besides, he's too old to be accepted. - Here, in the given above examples, 'besides' can be used as an adverb. - According to the explanation and example that are given above, 'Adverb' is the correct part of speech for the given above sentence.