In each of the following questions, choose the option that best completes the gap(s). It had been raining before the party started, _____

This question tests question tags. A question tag is a short question added to the end of a statement to seek confirmation. The rule is: the tag must use the same auxiliary verb as the main clause, and if the statement is positive, the tag must be negative (and vice versa).

The main clause is "It had been raining before the party started." The auxiliary verb here is had (part of the past perfect continuous: had been raining). Since the statement is positive, the tag must be negative: hadn't it?

The other options use the wrong auxiliary:

• isn't it? uses the present tense of "to be," which does not match the past perfect.
• wasn't it? uses the simple past of "to be," which would match a statement like "It was raining" but not "It had been raining."
• hasn't it? uses the present perfect auxiliary, which would match "It has been raining" but not the past perfect.

Always identify the auxiliary verb in the main clause first, then form the tag from the same auxiliary in the opposite polarity.