An adjective is a word that modifies or describes a noun. In the given sentence, "straight" does not modify any noun. Thus, option B is incorrect as well . An adverb is a word that modifies or adds more information about a verb or action. We can see that "straight" (which means 'directly' here) modifies the verb "went" in the sentence. Therefore option A is correct since "straight" works as an adverb. It then follows that option D is obviously incorrect.