Which question word to use?
We use who to ask questions about people:
Who is that?
Who lives here?
Who did you see?
We use whose to ask about possession:
Whose coat is this? [or] Whose is this coat?
Whose book is that? [or] Whose is that book?
Whose bags are those? [or] Whose are those bags?
We use what to ask questions about things:
What is that?
What do you want?
We use which to ask someone to choose something:
Which came first, the chicken or the egg?
I’ve got two books. Which do you want?
We can also use what and which with nouns:
What subjects did you study at school?
What newspaper do you read?
Which newspaper do you read – the Times or the Guardian?
Which book do you want?
Which one is yours?
Questions with prepositions:
Questions ending in prepositions are very common in English. After Who, Which or What we often have a preposition at the end of the sentence:
Who does this book belong to?
What are you looking for?
Which university did you go to?
What country do you come from?