50.What are the ________(原料)of making a cake?

49.How many people attended _________(庆典)?

48.The government should make laws to _______(废除)the abuse of power by the leaders.

47.The boys _________(闲逛) around the town with nothing to do.

46.The flowers will r_____ if you water then.

45.Careful maintenance can e_______ the life of your car by several years.

44.She _______(躲藏) herself away in her bedroom all day.

With the (26)_____________ (develop) of industry, air pollution is getting more (22)_________ more serious. In Beijing, many people suffer different kinds of illnesses because (28)_________ air pollution.

Air pollution is caused (29)_________ the following reasons: about half of the problem is caused by vehicles. There are more and more cars, buses on the roads, and they give (30)_________ poisonous gases. 25% of air pollution is caused by factories. Another (31)_________ (fact) is the smokers. Smoking not only does (32)_________ to

their health (33)__________ also to others. Besides these, about 10%of air (34)_____________ is caused by other reasons.

We should take some measures to fight (35)___________ pollution. New fuel can be used to replace gas. We can plant more trees. If everybody realizes the importance of environment and does something to stop pollution, the problem will be solved.