Answer:
They will wash the car, won't they?
Explanation:
A tag question usually comes after an independent clause. The tag question is most times attached with the intent of affirming the statement made in the independent clause. Our independent clause in the answer above is; "They will wash the car". The tag question, "Won't they?" is meant to affirm that statement.
Another example is, "They are going to school, aren't they?" In this example also, the independent clause makes a sentence that is to be confirmed by the tag question.
