interrogative pronoun

  edgood  —  Grammar Tips
We have various ways of asking questions in the English language. We can take a multiword verb form and put the subject between the auxiliary verb and the base infinitive, as in Do you mind? or Will he go? We can also use certain adverbs and ask questions like How do you feel? or Why did you fail? Finally, we can use interrogative pronouns to ask questions: who (subjective case), whom (objective case), whose (possessive case), which, and what. When we use these interrogative pronouns, the who-whom-whose will serve some grammatical noun function in the sentence. Pronoun case, therefore, becomes hugely important.

Keep an important point in mind: There are two kinds of questions (direct and indirect). You form a direct question by (1) putting the subject between the auxiliary verb and the main verb, (2) using an interrogative adverb, or (3) using an interrogative pronoun. Direct questions are followed by question marks. You form an indirect question by making a statement but omitting any signals of the direct question. In other words, you omit the question mark, as in He asked which book you like the most.

In the following examples of questions formed with interrogative pronouns, note the grammatical functions served by, and consequent case of, the who-whom-whose interrogative pronouns:
Interrogative Pronoun Question Grammatical Function
who Who's on first? The word who is the subject of the sentence (subjective case).
whom Whom should we call? The word whom is the object of call (objective case).
whose Whose turn is it? The word whose is the possessor of the noun turn (possessive case).
which Which runner won the race?
what What time is it?