Sharks Perform a Service for Earth's Waters
It is hard to get people to think of sharks as anything but a deadly enemy1. They are thought to1people frequently. But these fish2 perform a2service for earth's waters and for human beings. Yet business and sport fishing3 are threatening their3Some sharks are at risk of disappearing from 4
Warm weather may influence both fish and shark activity. Many fish swim near coastal areas5their warm waters. Experts say sharks may follow the fish into the same areas, 6people also swim. In fact, most sharks do not purposely charge at or bite humans. They are thought to mistake a person7a 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 the8when 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 smell4' It can find small amounts of substances in water, such as blood, body liquids and9produced by animals. These powerful10help sharks fred their food. Sharks eat fish, any11 sharks, and plants that live in the ocean.
Medical researchers want to learn more about the shark's body defense, and immune12against disease. Researchers know that sharks13quickly from injuries. They study the shark in hopes of finding a way to fight human disease.
Sharks are important for the world's14They eat injured and diseased fish. Their hunting activities mean that the numbers of other fish in ocean waters do not become too15.This protects the plants and other forms of life that exist in the oceans.
詞匯:
purposely adv.故意地，蓄意地 immune adj.免疫的
charge v.(向„„)沖(過去) jewelry n.珠寶
seal n. 海豹
注釋：
1.It is hard to get people tO think of sharks as anything but a deadly enemy：要讓人們相信鯊魚不是
(人類的)死敵不是一件容易的事。anything but意為“決不，遠非”，如：His performance in London is anything but a success.(她在倫敦的演出完全不成功。)
2.these fish：這些魚(指鯊魚)。fish單復數同形，如：0ne fish，two fish，many fish(見第二段第一句)。
3.sport fishin9：捕魚運動。
4.sense of smell：嗅覺
練習:
1. A attack B meet C love D visit
2. A terrible B eatable C valuable D possible
3. A source B existence C friends D fish
4. A Space B Sky C Land D Earth
5. A because B since C because of D by reason that
6. A whose B which C that D where
7. A to B for C like D with
8. A times B places C seas D oceans
9. A sciences B mathematics C chemicals D physics
10. A feelings B senses C touches D tastes
11. A those B these C another D other
12. A systems B processes C ideas D circles
13. A recover B reform C return D rely
14. A rivers B oceans C forests D mountains
15. A weak B little C few D great
答案與題解：
1.A本題應選擇attack，因為第一句說到：人們認為鯊魚是a deadly enemy，也就是說鯊魚會對人類造成傷害。第二句是對deadly enemy的具體說明。其他的三個選項meet，love，visit都不合適，love與上下文意思相反，meet和visit與上下文意思不符。
2.C空格2所在的句子由but連接，所以該句子表達的意思一定與第二句相反。第二句對鯊魚的評價是負面的，填入空格2的詞應該是正面的。四個選項中只有valuable符合這一條件，所以是答案。
3.B第三句說到鯊魚有益于“waters and human beings”，第五句又說到鯊魚瀕臨滅絕的危險。根據上下文的意思，threatening(威脅)到它們的應該是existence(生存)。其他的三個選項source，friends，fish都不合適，與上下文意思沒有聯系。
4.D如果鯊魚消失，從什么地方消失呢?當然從earth(地球)上消失。從space(宇宙空間)、sky(天空)中消失，或從land(陸地)上消失，都有悖常理。
5.C四個選項的意思都是“因為“，但是從用法上分析，because、since和by reason that之后要接句子，because of之后接名詞或名詞短語。their warm waters是名詞短語，所以要選用because of。
6.D“„people also swim”明顯是定語從句，其先行詞是表示地點的名詞area，所以要選關系副詞where.。
7.B從上下文判斷，本句的意思是：鯊魚將人錯認為是海洋動物。而“將„„錯認為是”的英語表達是mistake„for，所以本題的答案是選項B。
8.A本段的意思是：鯊魚并非故意襲擊人類。人們認為，由于鯊魚將人錯認為是海獅等海洋動物，在饑餓時才襲擊人類。日出和日落時，正是鯊魚饑腸轆轆的時候，人們不應該出海游泳。空格8填入的詞應該與時間有關，所以times是答案，而與地點有關的選項(places seas和oceans)與上下文意思脫節(jié)。
9.C本段第一、二句是說，鯊魚的嗅覺特別靈敏，能嗅到海水中存在的極為微量的氣味。作者舉了三個物質：血、體液和化學品?？崭?要填入表示物質的名詞。四個選項中惟一表達物質的詞是chemicals(化學品)。所以chemicals是答案，而其它三個選項與學科有關，脫離了上下文的意思，不是本題的答案。
10.B在第一、二句意思的基礎上，作者進一步說明，靈敏的嗅覺有助于鯊魚找到食物。所以本題的答案是選項D的senses，因為feelings，touches和tastes都與smells無關。
11.D 本句的中心詞是復數的sharks，another所修飾的名詞一般是單數，所以不會是答案。these和those是表特指的代詞，指代前面出現過的名詞。由于前面沒有先行詞，所以也不可能是答案。剩下的other是答案，any other sharks的說法也合乎英語的用法。
12.A從上下文判斷，醫(yī)學研究人員想要更多了解的是“身體抗病system(系統(tǒng))”，不會是“身體抗病idea(思想)”、“身體抗病工作(work)”或“身體抗病circle(周期)”。
13.A本段最后一句的意思是：醫(yī)學研究人員研究鯊魚的目的是為了找到一種人類抗病的方法。所以空格l3所在句子的意思應該是recover(quickly from injuries)?？茖W家想要探索的應該是有關受傷鯊魚recover quickly from injuries的秘密，而reform(改造)、return(回歸)和rely(依靠)只是與答案recover詞形上有點相似而已，其意思與上下文的意思風馬牛不相及。
14.B 從上下文判斷，鯊魚的存在能使0ceans得益。鯊魚不生活在rivers、forests或mountains中，所以，這三個選項不會是答案。
15.D本段的其余三句都是說明為什么鯊魚有益于海洋。它們吃海洋動物，結果使得海洋中的動物數量不會過多。weak、little、few都與上面表達的意思相反，所以，只有great是答案。