Concept:The correct interrogative word is chosen based on what is being asked about a person’s identity or profession.
Explanation:The sentence asks about the occupation or status of the person, not about a specific person already named.
The word “what” is used to ask about a thing, a job, or a description.
The words “whom” and “who” refer to persons in a subjective or objective sense, but here we need a complement describing the subject.
The word “which” is used when choosing from a limited set.
Thus, the natural question is: “If you insist that you are not a tailor, what are you?”
Answer:C. what