Concept:A question tag must agree with its main sentence in subject, tense, and auxiliary verb, and it usually changes from positive to negative or from negative to positive.
Explanation:The main sentence that this tag is meant to complete is not supplied in the question.
Option A,
isn’t it, would fit only a positive statement whose subject is
it and whose verb is the present tense of
to be.
Option B,
didn’t we, would require a past-tense main clause that uses an action verb and has
we as its subject.
Option C,
shouldn’t we, would require the modal verb
should in the main clause together with the subject
we.
Option D,
wasn’t it, would require a past-tense clause whose subject is
it and whose verb is
was.
Each option therefore points to a different subject, tense, and auxiliary verb.
In addition, a positive statement takes a negative tag, while a negative statement takes a positive tag.
This rule, however, can only be applied when the original statement is clearly known.
Since the main sentence is missing, no single option can be confirmed as the best completion.
Answer:Cannot be determined because the sentence to be completed is incomplete.