‘He knew my cousin.’ – ‘Which cousin?’
‘Who was your friend?’ – ‘What friend?’
who and whom
5.26 The pronoun who is used to ask questions about a person’s identity. Who can be the subject or object of a verb.
Who discovered this?
Who were her friends?
Who is Michael Howard?
Who did he marry?
In more formal English, whom is sometimes used instead of who as the object of a verb.
Whom shall we call?
Whom did you see?
Who and whom can also be the object of a preposition. When who is the object of a preposition, the preposition is put at the end of the clause.
Who did you dance with?
Who do I pay this to?
When whom is the object of a preposition, the preposition is put at the beginning of the clause, in front of whom.
For whom was he working while in Baghdad?
To whom is a broadcaster responsible?
So you report to who?
This use is especially common when you leave out part of the question.
‘They were saying horrible things.’ – ‘Really? To who?’
‘It could be difficult.’ – ‘For who?’
whose
5.27 Whose is used as a determiner or pronoun to ask which person something belongs to or is associated with.
Whose children did you think they were?
Whose coat was it?
Whose is that?
which
5.28 Which is used as a pronoun or determiner to ask someone to identify a specific person or thing out of a number of people or things.
Which is the best restaurant?
Which is her room?
Which do you like best?
Which doctor do you want to see?
When which is a determiner, it can be part of the object of a preposition. The preposition is usually put at the end of the question.
Which station did you come from?
Which character did you like most?
when and where
5.29 When is used to ask questions about the time something happened, happens, or will happen.
When did you find her?
When do we have supper?
Ginny, when are you coming home?
Where is used to ask questions about place, position, or direction.
Where does she live?
Where are you going?
Where do you go to complain?
why
5.30 Why is used to ask a question about the reason for something.
Why are you here?
Why does Amy want to go and see his grave?
Why does she treat me like that when we’re such old friends?
Why is sometimes used without a subject and with the base form of a verb, usually to ask why an action is or was necessary.
Why wake me up?
Why bother about me?
Why make a point of it?
Why not can be used with the base form of a verb, in order to make a suggestion or to ask why a particular action has not been taken.
Why not end it now?
Why not read a book?
If you have money in the bank, why not use it?
how
5.31 How is usually used to ask about the method used for doing something, or about the way in which something can be achieved.
How do we open it?
How are you going to get that?
How could he explain it to her?
How did he know when you were coming?
How is also used to ask questions about the way a person feels, about the way someone or something looks, or about the way something sounds, feels, or tastes.
How are you feeling today?
‘How do I look?’ – ‘Very nice.’
How did you feel when you stood up in front of the class?
how with other words
5.32 How can be combined with other words at the beginning of questions.
How many and how much are used to ask what number of things there are or what amount of something there is.
How many is followed by a plural countable noun.
How many people are there?
How many languages can you speak?
How many times have you been?
How much is followed by an uncountable noun.
How much money have we got in the bank?
Just how much time have you been devoting to this?
How many and how much can be used without a following noun when you do not need to make it clear what sort of thing you are talking about.
How many did you find?
How much did he tell you?
How much does it cost?
How much do they really understand?
How long is used to ask about the length of a period of time.
How long have you lived here?
How long will it take?
How long can she live like this?