Interrogative Determiners

what, which, whose

The interrogative determiners are: what, which, whose

Whose	iPad did you use?
	car keys are these?
What	stupid man told you that?
	books did you read?
Which	red pen do you want?
	three teachers do you prefer?

Whose means "belonging to which person": They didn't know whose car it was.

What is for asking for information specifying something: What time did you arrive? I wonder what reason he gave.

Which is for asking for information specifying one or more people or things from a definite set: Which table would you prefer? I wonder which teacher told him that.

Like all determiners, interrogative determiners come at the beginning of a noun phrase, so they come in front of any adjective(s).

Look at these example sentences:

Whose iPhone was stolen?
He couldn't remember whose car keys they were.
What idiot told you that?
I don't know what non-fiction books he was reading.
I asked them which Italian car was best.
Which nightclubs on the Champs Elysées did you go to?

1. Note that whose functions both as an interrogative and a possessive determiner, so technically whose is an interrogative possessive determiner. Whose is the only interrogative possessive determiner in English.

2. Note also that there is NO apostrophe (') in the determiner whose. The contraction who's (meaning "who is" OR "who has") sounds exactly like whose and even native speakers frequently confuse the two.

I wonder whose dog that is.
Peter, who's not here, is Thai. (who is)
Marie, who's just left, is French. (who has)