用所给动词的正确形式填空。 1. By the time we got to the airport, the plane _______ (take) off. 2. The children ________ (have) the book for two weeks before they returned it to the library. 3. He ______ (study) English for five years before he came here. 4. When I woke up this morning, I found that it ________ (stop) snowing. 5. The boy _____ (not watch) the movie because he had watched it twice. 6. Kate told me that it was the second time that she _______ (go) skating. 7. When Jim _____ (come) to China two years ago, he found people didn't understand him at all though he had learnt some Chinese in his own country. 8. I saw Han Mei yesterday. We _____ (not see) each other since we left Beijing. 9. If you _______ (work) harder, you would have passed the examination. 10. No sooner had we got there than it ______ (begin) to rain.