29. Don’t let one failure d　　　　　　　　 　(气馁) you, try again.

28. He used to be a heavy smoker, but we manage to p　　　　　　　 (说服)him to stop smoking.

27. He is so tired that he has not enough s　　　　　 _____　　 　(力气) to walk on.

26. Normally, people and animals that are d　 　　　　　　　　　(无防备的) are weak and unable to protect themselves from attack.

25. He doesn’t often get flu, but when he does he really s　　　　　　　 　(痛苦).

24. Simon is not a　　　　　　　　 　(可达到的) at the moment. Should I ask him to call you back?

23.The virus is t　 　　　　　　　(传染) via physical contact.

22.One of the boys in the class had a fever and he soon i　　　　　　 　(感染) other children.

21.V　　　　　 (病毒)cause illnesses such as the common cold, flu and measles.

20.When a pencil is partly in a glass of water , it looks as if it ______.

　　 A. break　 B. has broken　 C. were broken　 D. had been broke