Wh-Questions With Who, Whom, Which, How and Whose

A. Who refers to people, and can be used as subject, object or complement: 

• Who owns that car?
• Who did you meet?
• Who was her father?

Whom is used as a formal alternative to who as object, and also directly after prepositions:

• Whom did you meet?
• Whom were you talking to?

Which is used to refer to people when we want to identify somebody in a group (for example, in a crowded room or in a photograph):

• 'Which is your brother?' "The one next to Ken.'

and we can use which instead of who to talk about particular classes of people:

• Which do you think earns more, a teacher or a police officer? (or Who do you think...?)

B. We usually use which, rather than who or what, in questions before one(s) and of, as which is commonly used to ask or talk about a choice between one or more things:

• I've decided to buy one of these sweaters. Which one do you think I should choose?
• Which of you would like to go first? (rather than Who of...?)

C. When we use who or what as subjects, the verb that follows is usually singular, even if a plural answer is expected:

• Who wants a cup of coffee? (said to a number of people; not Who want a cup of coffee?)
• What is there to do in Birmingham at Christmas? (expects an answer giving a number of things to do; not What are there to do in Birmingham at Christmas?)

However, the verb can be plural in echo questions after a plural subject or a subject consisting of two or more noun phrases joined by and:

• Mr Smith and his family are here to see you.' 'Who are here?' (or Who's here?) and when who and what function as complements:
• Who are those people over there?
• What are the consequences of the decision?

D. We use how, not what, to ask -
- a general opinion on something (e.g. How is the journey?) 
- about general health (e.g. How is your brother?)
- about preferences relating to food and drink (e.g. How do you like your coffee?)

We use what, not how, to ask -
- a general opinion on something with What... like? (e.g. What was your journey like?) 
- for details with What... like/hate (etc.) about...? (e.g. What do you like about your job?) 
- about the consequences of something with What if...? (e.g. What if your plan doesn't work?)
- about the naming of something in the question (e.g. What is it called?)

We use either what or how -

-  to make a suggestion with What/How about...? (e.g. How/What about having a swim?) 
- to ask for more information in the question How/What do you mean? (e.g. There's something wrong with the car.' 'Something wrong? How/What do you mean?') 

E. We can use whose to ask about the person that owns or is responsible for something. Whose can be used either before a verb (as a pronoun):

• Whose are these boots?

or before a noun or noun phrase (as a determiner) introducing direct or indirect questions:

• Whose boots are these?
• She asked me whose coat I was wearing. 

In formal contexts we can use a preposition before whose: 

• In whose desk was it found? (less formally Whose desk was it found in?

However, in questions without a verb a preposition comes before whose:

• 'We're meeting at nine.' 'In whose house?' (not Whose house in?)

Try this exercise to test your grammar.

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