单选题

Sharks Perform a Service for Earth's Waters

It is hard to get people to think of sharks as anything but a deadly enemy. They are thought to (51) people frequently. But these fish perform a (52) service for earth's waters and for human beings. Yet business and sport fishing are threatening their (53) . Some sharks are at risk of disappearing from (54) .
Warm weather may influence both fish and shark activity. Many fish swim near coastal areas (55) their warm waters. Experts say sharks may follow the fish into the same areas, (56) people also swim. In fact, most sharks do not purposely charge at or bite humans. They are thought to mistake a person (57) a sea animal, such as a seal or sea lion. That is why people should not swim in the ocean when the sun goes down or comes up. Those are the (58) when sharks are looking for food. Experts also say that bright colors and shiny jewelry may cause sharks to attack.
A shark has an extremely good sense of smell. It can find small amounts of substances in water, such as blood, body liquids and (59) produced by animals. These powerful (60) help sharks fred their food. Sharks eat fish, any (61) sharks, and plants that live in the ocean.
Medical researchers want to learn more about the shark's body defense, and immune (62) against disease. Researchers know that sharks (63) quickly from injuries. They study the shark in hopes of finding a way to fight human disease.
Sharks are important for the world's (64) . They eat injured and diseased fish. Their hunting activities mean that the numbers of other fish in ocean waters do not become too (65) . This protects the plants and other forms of life that exist in the oceans.

单选题 A. attack B. meet C. love D. visit

【正确答案】 A

【答案解析】[解析] 本题应选择attack，因为第1句说到：人们认为鲨鱼是a deadly enemy，也就是说鲨鱼会对人类造成伤害。第2句是对deadly enemy的具体说明。其他的3个选项meet、love和visit，都不合适，love与上下文意思相反，：meet和visit与上下文意思不符。

单选题 A. terrible B. eatable C. valuable D. possible

单选题 A. source B. existence C. friends D. fish

单选题 A. Space B. Sky C. Land D. Earth

单选题 A. because B. since C. because of D. by reason that

单选题 A. whose B. which C. that D. where

单选题 A. to B. for C. like D. with

单选题 A. times B. places C. seas D. oceans

【正确答案】 A

【答案解析】[解析] 本段的意思是：鲨鱼并非故意袭击人类。人们认为由于鲨鱼将人错认为是海狮等海洋动物，才会在饥饿时袭击人类。日出和日落时，正是鲨鱼饥肠辘辘的时候，人们不应该出海游泳。该空填入的词应该与时间有关，所以times是答案，而与地点有关的选项(places、 seas和oceans)与上下文意思脱节。

单选题 A. sciences B. mathematics C. chemicals D. physics

【正确答案】 C

【答案解析】[解析] 本段第1、2句是说鲨鱼的嗅觉特别灵敏，能嗅到海水中存在的极为微量的气味。作者列举了3种物质：血、体液和化学品。该空要填入表示物质的名词。4个选项中唯一表达物质的词是chemicals(化学品)。所以chemicals是答案，而其他三个选项与学科有关，脱离了上下文的意思，不是本题的答案。

单选题 A. feelings B. senses C. touches D. tastes

单选题 A. those B. these C. another D. other

【正确答案】 D

【答案解析】[解析] 本句的中心词是复数的sharks，another所修饰的名词一般是单数，所以不会是答案。 these和those是表特指的代词，指代前面出现过的名词。由于前面没有先行词，所以它们也不可能是答案。所以答案只能是剩下的other，而any other sharks的说法也合乎英语的用法。

单选题 A. systems B. processes C. ideas D. circles

单选题 A. recover B. reform C. return D. rely

【正确答案】 A

【答案解析】[解析] 本段最后一句的意思是：医学研究人员研究鲨鱼是为了找到一种人类抗病的方法。该空所在句子的意思应该是recover (quickly from injuries)。科学家想要探索的应该是有关受伤鲨鱼recover quickly from injuries的秘密，而reform(改造)、return(回归)和rely(依靠)只是与答案recover在词形上有点相似，与上下文的意思风马牛不相及。