填入适当的词。

1. I haven't heard from him_______ he went to America.

2.He won't be here_______ he is invited.

3. He will not go to the cinema______ he is very busy.

4. We found the key_______ she had left it.

5. We found the books two days ______he had gone away.

6. We had no sooner got to the station ________the train left.

7. He speaks English ______ he were an Englishman.

8.He is explaining clearly______  they can understand.

9. Do not leave the room______ you have finished the test.

10. She sang______ she went along.