过去完成时态

I had finished my homework before I went out to play.

They had already left when I arrived at the station.

She had learned the entire lesson by heart.

与过去事实相反的虚拟语气

If I had studied harder, I would have passed the exam.

They had better have stayed at home instead of going out in such weather.

She had better not have said that to him.

过去完成时的被动语态

The book had been borrowed by him before I returned it.

The house had been cleaned by her every day.

The meeting had been scheduled for 3 PM.

这些句子分别展示了"had"在不同语境下的用法，包括过去完成时态、虚拟语气和被动语态。希望这些例子能帮助你更好地理解和运用"had"。