The correct answer is 'Adjective'. Key Points - Here, in the given above sentence, the underlined part "questionable" is used as an adjective. - As per the general rule, adjectives are words that describe the qualities or states of being of nouns. - Example: - I haven't seen them since that memorable evening when the boat capsized. - Do you have anything breakable in your bag? - Here, in the given above examples, 'memorable and breakable' can be used as an adjective. - According to the explanation and example that are given above, 'Adjective' is the correct part of speech for the given above sentence.