The policeman, . . . . . . . . caught the thief, is a very brave man. A. whom B. whose C. which D. who

The correct answer is D. who.

The sentence is about the policeman, and we are trying to identify the policeman. The policeman is the subject of the sentence, and the verb is “caught.” The pronoun “who” is used to refer to the subject of a sentence.

A. whom is used to refer to the object of a sentence. In this sentence, the object is “the thief.”

B. whose is used to refer to possession. In this sentence, there is no possession being referred to.

C. which is used to refer to non-human things. In this sentence, the policeman is a human.

I hope this helps!