Past perfect

Affirmative Sentence

Subject+had+past participle

They had finished before I arrived.

Negative Sentences

Subject+had+not (hadn`t)+past participle

We hadn't eaten before he finished  the job.

Questions Sentences

Questions word+had subject+past participle?

What did she thought before I asked the question?


Practice http://www.perfect-english-grammar.com/past-perfect-exercise-1.html