The following questions are regarding how a verb have is to be handled in a tag question. GMATCLUB grammar mentions - " The verb have can be used as the main verb (I have a headache), or as an auxiliary verb (Jenny has received her diploma). When have functions as the main verb, a form of do, does, or did must be used (You have a headache, don’t you?)"
Now, let look at some of the questions from Exercise 19:
1. We’ve already taken that test, ______________________?; the answer given is "haven't we" (why is "didn't we" not used here. Is it because of the presence of another verb "taken"?)
2. You have been to Washington D.C., ______________________?; the answer given is "haven't you" (why is "don't you" not used here. Is it because of the presence of another verb "been"?)
Notice the difference between sentences:
a headache", don’t you?
that test",havent we?
"You have been
to Washington D.C". haven't you?
In the first sentence there is only one verb - have. In other two sentences role of 'have' is merely to mark the tense(function as auxiliary verb) for the actual verbs 'take' and 'be' respectively.Thus the difference between 1st and other two.
Hope it helps.
Got it. Thanks for clarifying!