17．A. learned B. taught C. offered D. heard 　　18．A. harder B. earlier C. later D. easier 　　19．A. business B. transport C. travel D. hotel 　　20．A. interesting B. crowded C. famous D. noisy （二）阅读理解

　　Parts of Africa are covered by a dark cloud. But this is no rain cloud. It is a living cloud made of billions of locusts that are travelling across the continent eating everything in their path.

　　And now in the battle to stop this disaster, a radio station in Senegal, West Africa, is offering listeners 50 kilograms of rice if they can catch and kill 50 kilograms of locusts. "We think this idea will get more people involved in the war on the locusts," said Abdoulaye Ba, from Sud-Fm, a radio station in one of Senegal's worst affected regions.

　　This is West Africa's biggest locust disaster in 15 years, and it is moving east, causing huge damage to crops. As they move they breed and increase their number and will soon threaten Sudan in the northeast of Africa. Some say it could reach Asia.

　　Experts say the harmful effect on crops in areas already suffering from food shortage and war could cause many people to go hungry. Governments in the region are not well equipped to fight the pest.

　　Although leaders of 12 countries have agreed on a plan, it may be inadequate. "We are now treating 6,000 hectares per day with pesticide (杀虫剂), but we need to treat 20,000 hectares per day in order to have any hope of controlling this disaster," said Mohamed Abdallahi Ould Babah, director of locust control in Mauritania.

　　Requests are being made for international aid, which is the only way to limit the crisis (危机), the UN's Food and Agriculture Organization warned.

1. By using "dark cloud" to describe locusts in the first paragraph, the writer ____.

A. showed vividly the size and speed of the mass of locusts

　 B. suggested the great damage that locusts can cause

　 C. warned that locusts would sweep the continent like rain clouds

　 D. both A and B

2. The story is about _____.

A. West Africa's united effort in fighting a disaster

　 B. the difficulty in controlling locusts

　 C. how locusts caused great damage to West Africa

　 D. a struggle to fight against a disaster posed by locusts in West Africa

3. The locust disaster _____.

A. would be even more serious in Asia B. is (was) out of control