Page 643 - Practical English Usage 3ed - Michael Swan, Oxford

which, what and who: question words 622
4 subject, complement and adverbial clauses
When a question-word clause is a subject or complement, whether is normally
preferred.
Whether we can stay with my mother is another matter. (subject) The question is wlwtlwr tlw man can be trusted. (complement)
The question is if... is also possible, but less common. The question is ifthe man can be trusted.
5 not used in echo questions
lfand whether are not normally used in 'echo questions' (see 483).
Are you happy?-Am I happy? No! (NOT •• •-If/Whether Pm httppy? ..)
622 which, what and who: question words
1 which and what: the difference
Which and what are often both possible, with little difference of meaning. WhichlWhat is the hottest city in the world?
WhichlWhat train did you come on?
WhichlWhat people have influenced you most in your life?
We prefer which when we have a limited number of choices in mind. We've got white or brown bread. Which will you have?
(More natural than . .. What will you have?) Which size do you want - sman medium or large?
When we are not thinking of a limited number of choices, what is preferred. What language do they speak in Greenland?
(More natural than Which language . ..)
What's your phone number? (NOT Vlhieh is )'Bur "heme nftmber?)
2 determiners: which and what
Before nouns, which and what can be used to ask questions about both things and people.
Which teacher do you like best?
Which colour do you want - green, red, yellow or brown?
What writers do you like? What colour are your baby's eyes?
3 which of
Before another determiner (e.g. the, my, these) or a pronoun, we use which of. Who and what are not normally used with oflike this in modem English.
Which ofyour teachers do you like best? (NOT Wh6fWlt~tOf)'BftF tefiehers . ..) Which ofus is going to do the washing up? (NOT l'1h6 ofrtS ...?)
Which ofthese coats is yours? (NOT Ylhtlt ofthese ...?)
4 without nouns: who for people
When these words are not followed by nouns or pronouns, we generally use who, not which, for people.
Who won - Smith or Fitzgibbon? (NOT Whie,; ftffln ...?) Who are you going out with - Lesley or Maria?
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