Tag questions

Affirmative
(a) You know Bob Wilson
(b) Marie is from Paris
(c) Jerry can play the piano
Negative
(d) You don’t know jack smith
(e) Marie isn’t from Athens
(f) Jerry can’t speech Arabic
Negative
Don’t you?
Isn’t she?
Can’t he?
Affirmative
Do you?
Is she?
Can he?
A tag question is a question that is added onto the end of a sentence. An auxiliary verb is used in a tag question.
When the main verb is affirmative, the tag question is negative.
When the main verb is negative, the tag question is affirmative.
 In using tag question, a speaker gives his idea while asking a question at the same time. In (g) and (h) below: I (the speaker) use a tag question because I expect you (the listener) to tell me that my information or my idea is correct. As with other kinds of questions, a speaker usually uses a rising intonation at the end of a tag question.
(g) I think that you know bob Wilson (The speaker’s idea)
You know bob Wilson, don\t you? (The speaker’s question)
Yes, I do (Expected answer)
(h) I think that you don’t know jack smith (The speaker’s idea)
You don’t know jack smith, do you? (The speaker’s question)
No, I don’t (Expected answer)
Compare
(i) A: Do you know Tom Lea? (a yes no/no question)
B: Yes, I do Or No, I don’t
(j) A: You know tom lea don’t you? (a tag question)
B: Yes, I do.
In (i): The speaker has no idea. The speaker is simply looking for information.
In (j): The speaker believe that the listener knows tom lee. The speaker wants to make sure that his idea is correct.