1．构成：had been + 现在分词
2．功能：表示过去某个时间之前一直在进行的动作。
She said that she had been typing a paper before I came in.
比较：
The girl had cleaned up the room, so it was tidy.
The girl had been clearing up the room, so we had to wait outside.
练习
1. It ________ for four days when we arrived, so the roads were very muddy.
A. was raining B. would be raining C. had been raining D. has rained
2. He told us that he ________ there since 1982.
A. has been living B. had been living
C. would have lived D. was living
3. He had been learning English for 3 years before he came here and ________ now.
A. is still learning B. had been learning
C. was still learning D. has been learning
4. By the end of last week, he ________ in the company for 10 years.
A. had worked B. had been working
C. will have worked D. would have worked
5. Not until then did people know that he ________ important military information to the enemy for a long time.
A. sold B. would sell C. had sold D. had been selling
参考答案：1.C；2.B；3.A；4.B；5.D
