2. She will sing a song ____ she is asked.

　　　 A. if　　　　　　　　　　　　　　 B. unless　　　　　　　 C. for　　　　　　　　　　 D. since

1. I’ll let you know ____ he comes back.

　　　 A. before　　　　　　　 B. because　　　　　　 C. as soon as　　　　　 D. although

18. Hard _________ he tried, he couldn’t force the door open.

17. The boy was so tired __________ he fell asleep on the bus.

16. __________ you lock all the doors, he can still manage to get in.

15. He was angrier __________ ever before.

14. The meeting became so disorderly __________ the speaker had to shout the audience down.

13. We're doing everything we can to make things as easy for you ___________we can.

12. She wouldn't forget her mother's birthday __________ she seldom wrote to her family.

11. We would try to get a car __________we could all travel together more easily.