一段时间的状语，就只能表示动作的完成，而现在完成进行时则表示动作的延续。试比较：

They have built a new lab.

他们建造了一幢新的实验室。(表示动作的完成)

They have been building a new lab (these years).

他们(这几年)一直在建造一幢新的实验室。(无论用时间状语还是不用时间状语，都表示动作的延续)

Step IV Practice （Using Structures in Workbook）

一、单项选择。

1. How long have you been 　　　 here?

　A. stood　　　　B. to stand

　C. standing　　　D. stands

2. The student has been 　　　 the novel since he finished school.

　A. wrote　　　　B. writing

　C. written　　　 D. writes

3. - Hi, David! Are you tired?

　　- Yes, I am tired. I 　　　 the classrooms for 4 hours.

　　A. am cleaning　　　　　B. was cleaning

　　C. have been cleaning　　　　D. had cleaned

4. Where have you been? We 　　　　 you everywhere.

　　A. have been looking for

　　B. has looked for

　　C. had looked for

　　D. has been looking for

5. - It 　　 for nearly a week. Will it last long?

　 - No, it's reported that we'll have a fine weekend.

　A. have rained　 B. has been raining

　C. rains　　 D. rained

二、句型转换。

1. He has been watching the interesting play for two hours. (改为否定句)

He 　　　 　　　 watching the interesting play for two hours.

2. I have been learning English for two years. (改为一般疑问句并作否定回答)

- 　　　 you 　　　 learning English for two years?

- No, I 　　　.

3. My brother has been collecting stamps for five years. (对划线部分提问)

　　　 has your brother been 　　　 for five years?

4. The boy has been listening to the music videos since he was eight years old. (对划线部分提问)

　　　 　　　 has the boy been listening to the music videos?

5. She has been working in the hospital for six years. (对划线部分提问)

　　　 　　　 she been working for six years?　　

Step V Homework

Ask the students finish Exercise in workbook: Using Words and Expressions and Using