Page 504 - Practical English Usage 3ed - Michael Swan, Oxford

question tags (2): advanced points 488
5 it and they with nothing, nobody, somebody etc
We use it in question tags to refer to nothing and everything. Nothing can happen, can it?
We use they (see 528) to refer to nobody, somebody and everybody (and no one etc).
Nobody phoned, did they?
Somebody wanted a drink, didn't they? Who was it?
6 non-auxiliary have
After non-auxiliary have (referring to states), question tags with have and do are often both possible. (Do is normal in American English.)
Your father has a bad back, hasn't/doesn't he? For more about the use of do with have. see 236-239.
7 'same-way' question tags: You're getting married, are you?
Non-negative question tags are quite common after affirmative sentences. These are often used as responses to something that has been said, like 'reply questions' (see 484): the speaker repeats what he/she has just heard or learnt, and uses the tag to express interest, surprise, concern or some other reaction.
So you're getting married, are you? How nice!
So she thinks size's going to become a doctor, does she? Wen well. You think you're funny, do you?
'Same-way' tags can also be used to ask questions. In this structure, we use the main sentence to make a guess, and then ask (in the tag) if it was correct.
Your mother's at home, is she? This is the last bus, is it?
You can eat shellfish, can you?
I'll ... shall I? can be used to make offers.
I'll hold that for you, shall I?
Negative 'same-way' tags are occasionally heard; they usually sound aggressive.
I see. You don't like my cooking, don't you?
8 ellipsis: Nice day, isn't it?
In sentences with question tags, it is quite common to leave out pronoun subjects and auxiliary verbs. (This is called 'ellipsis'. For details, see 179.)
(It's a) nice day, isn't it? (She was) talking to my husband, was she?
In very informal speech, a question tag can sometimes be used after a question with ellipsis.
Have a good time, did you? Your mother at home, is she? John be here tomorrow, will he?
For detalls of other kinds of tags. see 514.
9 I (don't) think
Note the use of question tags in sentences beginning with 1 (don't) think and similar expressions (see 179).
I think he's Norwegian, isn't he? (NOT ••• tum'r:?) 1 don't think it will rain, will it? (N OT • • • titJ P.)
1 suppose you're hungry, aren't you?
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