31. A. notice 　　　　　　　　　　　 B. believe in 　　　　　　　　　　　 C. doubt 　　　　　　　　　　　　　 D. guess at

29. ______ we are still not clear is ______ the universe came into being.

　 A. That; what　　 B. What; that　　 C. What; how　　 D. That; how

28. In peace, too, the Red Cross is expected to send help ______ there is human suffering.

　 A. whoever　　 B. however　　 C. whatever　　　 D. wherever

27. He was about halfway through his meal ______ a familiar voice came to his ears.

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

26. Most birds find it safe to sleep in the trees, but ______ they have eggs or young chicks, they don’t use a nest.

　 A. why　　 B. how　　 C. unless　　 D. where

25. -Mom, what did your doctor say?

- He advised me to live ______ the air is fresher.

A. in where　　 B. in which　　 C. the place where　　 D. where

24. Generally speaking, ______ according to the directions, the drug has no side effect.

　 A. when taking　　 B. when taken　　 C. when to take　　 D. when to be taken

23. You should try to get a good night’s sleep ______ much work you have to do.

　 A. however　　 B. no matter　　　 C. whatever　　 D. no matter what

22. ______ it with me and I’ll see what I can do.

　 A. When left　　 B. Leaving　　 C. If you leave　　 D. Leave