Topic: Interchange of Parts of Speech,

Best Answer Explained in Below-:

The adjective form of the noun "question" is "questionable." Understanding this requires examining what qualifies as an adjective and how it relates to nouns. The word "question" itself can function as a noun, representing an inquiry or an expression of doubt. However, when we look for an adjective form, we seek a word that describes a quality associated with questions or their nature.

"Questionable" derives from the root word "question," and it specifically refers to something that is open to doubt or requires scrutiny; it describes situations or information that may not be reliable or that provoke uncertainty. For example, if a claim is described as questionable, it implies that it warrants further investigation or skepticism.

While "questioning" is also an adjective, it typically describes the act of inquiring or expressing doubt and does not specifically denote something that is inherently related to the noun "question" in the sense of being doubtful or problematic. Therefore, among the options provided, "questionable" is the most appropriate adjective form of "question," as it closely aligns with the nuances associated with questioning or doubt itself.