Read the sentence. the administrator of the company, the woman overseeing the department, added new personnel to better augment the existing sales force. which part of the sentence functions as an adverb? of the company overseeing the department to better augment existing sales force

Based on the given sentence above, the part of the sentence that functions as an adverb is " to better augment existing sales force". When we say adverb, this is a word or group of words that modifies an adjective, verb or adverb. In this case, it modifies the verb "added". Hope this answers your question.

C.they are verbs.

Compare who exactly?