Part B

　　一、完形填空(共20小题;每小题1.5分,满分30分)

　　Sharks have lived in the oceans for over 450 million years,long before dinosaurs appeared.There are now about 360 　1　 of sharks,whose size,behavior,and other characteristics differ widely. 

　　Every year,we catch and kill over 100 million sharks,　2　 for food and for their fins.Dried shark fins are used to make shark fin soup,which 　3　 for as much as $50 a bowl in fine Hong Kong 　4　.Other sharks are killed for sport and out of fear.Sharks are vulnerable(脆弱的) to overfishing because it 　5　 most species 10 to 15 years to begin reproducing and they 　6　 only a few young babies. 

　　7　 by movies and popular novels,most people see sharks as people-eating animals.This is far from the 　8　.Every year,a few types of shark injure about 100 people worldwide and kill about 25.Most 　9　 are by great white sharks,which often feed on sea lions and other marine mammals.They sometimes mistake human swimmers for their normal food,　10　 if they are wearing black wet suits.If you are a typical ocean-goer,your 　11　 of being killed by an unprovoked(无缘无故的)attack by a shark are about 1 in 100 million.You are more 　12　 to be killed by a pig than a shark and thousands of times more likely to get killed when you drive a car. 

　　Sharks help 　13　 human lives.In addition to providing people with food,they are helping us learn how to 　14　 cancer,bacteria,and viruses.Sharks are very healthy and have aging processes similar to ours.Their highly effective immune system 　15　 wounds to heal quickly without becoming infected,and their blood is being studied in 　16　 with AIDS research.Sharks are among the few animals in the world that almost 　17　 get cancer and eye cataracts.Understanding why can help us improve human 　18　. 

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