Explanation

The keyed answer is (D) Pronoun, which fits if the word actually underlined in the original paper was "She" ("She truthfully answered …"). As transcribed here the bold falls on "truthfully," which modifies "answered" and is therefore an adverb — and "Adverb" is not even among the options — so the underline appears mis-transcribed. Both reputable keys nevertheless mark (D), which is retained: key disputed.