They understood that they....a mistakea)madeb)makec)had maded)are making

They understood that they had made a mistake.

Они поняли, что сделали ошибку.

Did they understand that they had made a mistake?

Did the understand or forget that they made a mistake?

What did they understand?

What had they made?

Who understood that they had made a mistake?

Who had made a mistake?

They understood that they had mad a mistake, didn\'t they?