7. They will never succeed, _____ hard they try.

A. because　　　 　　　 B. however　　　　　　 C. when　　　　　　　　 D. since

6. It is about ten years _____ I met you last.

A. since　　　　 B. for　　　　　　　　　　 C. when　　　 　　 D. as

5._____ you go, don't forget your people.

A. Whenever　　 B. However　　　　　 C. Wherever　 　　 D. Whichever

4. Read it aloud _____ the class can hear you.

A. so that 　　　　　　 B. if　　　　　　　　　　　 C. when　　　 　　 D. although

3. We will work ____ we are needed.

　　　 A. whenever　　　　　 B. because　　　　　　 C. since　　　　　 　　　 D. wherever

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.