用so, to, because 填空。

1. I didn't come out early, __________ I missed the early bus. 

2. She went there __________ work as a librarian.

3. It was quite late, __________ we decided to go home.

4. He must be a good student, __________ he always do something well.

5. It's not difficult for you __________ learn English if you work hard in the right way.

6. I was very tired, __________ I went to bed early.

7. He bought a lot of presents __________ make his mother happy.

8. _________ know about English is one thing, and to know English is quite another.

9. He didn't come to school, __________ he was ill yesterday.

10. They are having an important meeting, __________ you can't go into the room.