He had taken the exam last year. 他去年已经考过这个试。
I had been to America. 我曾去过美国。
They had visited a doctor. 他们已经看过医生了。
A thief had stolen my watch. 小偷偷走了我的手表。
It had rained heavily last month. 上个月雨下得很大。
The students had gone before the teacher came in. 老师进来以前学生们已经走了。