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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 to1people frequently. But these fish perform a2service for earth's waters and for human beings. Yet business and sport fishing are threatening their3.Some sharks are at risk of disappearing from4.
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 the8 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 wa-ter,such as blood,body liquids and9 produced by animals. These powerful10help sharks find their food. Sharks eat fish,any11sharks,and plants that live in the ocean.
Medical researchers want to learn more about the shark's body defense,and immune 12against 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's14.They 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.
8._________
A: times
B: places
C: seas
D: oceans

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共用题干
Global Warming
Few people now question the reality of global warming and its effects on the world's climate. Many scientists1the blame for recent natural disasters on the increase2the world's temperatures and are convinced that,more than3before,the Earth is at4from the forces of the wind,rain and sun.5to them,global warming is making extreme weather events,6as hurricanes and droughts,even more7and causing sea levels all around the world to8.
Environmental groups are putting9on governments to take action to reduce the 10 of carbon dioxide which is given 11 by factories and power plants,thus attacking the problem at its source. They are in12of more money being spent on research into so-lar,wind and wave energy devices,which could then replace existing power13.
Some scientists,14believe that even if we stopped releasing carbon dioxide and other gases into the atmosphere tomorrow,we would have to wait15hundred years to notice the results. Global warming,it seems,is here to stay.
15._________
A: several
B: over
C: numerous
D: various
Her strange behaviour aroused our suspicions.
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Robots may Allow Surgery in Space
Small robots designed by University of Nebraska researchers may______(51)doctors on Earth to help perform surgery on patients in space.
The______(52),wheeled robots,which are about 3 inches tall and as wide as lipstick case, can be slipped into small incisions and computer-controlled by surgeons in different______(53). Some robots are equipped with______(54)and lights and can send images back to surgeons and others have surgical tools attached that can be controlled______(55).
"We think this is going to replace open surgery," Dr. Dmitry Oleynikov said at a news ______(56).Oleynikov is a specialist in computer-assisted surgery at the University of Nebraska Medical Center in Omaha.
Officials hope that NASA will teach______(57)to use the robots soon enough so that surgeries could one day be performed in space.
On earth,the surgeons could control the robots themselves from other locations.For example, the robots could enable surgeons in other places to work on injured______(58)on the front line. Researchers plan to seek federal regulatory approval early next year. Tests on______(59)have been successful,and tests on humans in England will begin very soon.
The camera-carrying robots can provide views of______(60)areas and the ones with surgical tools will be able to maneuver inside the body in______(61)surgeons' hands can't. The views from
the camera-carrying robots are better than the naked eye,because they send back color images that are______(62).Because several robots can be inserted through one incision,they could reduce the amount and______(63)of cuts needed for surgery,which would decrease______(64)time. This is particularly helpful to those patients who have been debilitated by long illness.
______(65),Oleynikov said,the tiny robots may enable surgeons to work without even placing their hands in patients' bodies."That's the goal,"Oleynikov said."It's getting easier and easier. We can do even more with these devices.
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The Greatest Mystery of Wha1eg
The whale is a warm一blooded,air-breathing animal,giving birth to its young alive,sucking them一and,
like all mammals,originated on land. There are many__________(51)of this. Its front flippers (鳍状肢),
used for steering and stability,are traces of feet.
Immense strength is________(52)into the great body of the big whales,and in fact most of a
whale',body is one gigantic muscle.The blue whale'S pulling strength has been estimated________.(53)
400 horsepower. One specimen was reported to have towed(拖)。whaling vessel for seven hours at the
_______(54)of eight knot(节).
An angry whale will________(55).A famous example of this was the fate of Whaler Essex,
________(56)was sunk off the coast of South America early in the last century.More recently,steel ships
have_(57)their plates buckled(使弯曲)in the same way. Sperm whales(抹香鲸)were known
to seize the old-time whaleboats in their jaws and crush them.
The greatest________(58)of whales is their diving ability.The sperm whale dives to the bottom for
his________(59)food,the octopus(章鱼),In that search he is known to go as far down as 3 , 200 feet,
where the________(60)is 1,400 pounds,to a square inch.Doing so he will________(61)underwa-
ter as long as one hour. Two special skills are involved in this storing up enough________(62)(all
whales are air-breathed)and tolerating the great change in pressure.Just how he does it scientists have not
_________(63).It is believed that some of the oxygen is stored in a special________(64)of blood
vessels,rather than just held in the lungs.And it is believed that a special kind of oil in his head is some sort
of a compensating mechanism that_________(65)adjusts the internal pressure of his body.But since you
can't bring a live whale into the laboratory for study,no one knows just how these things work.
_________(54)
A: number
B: degree
C: distance
D: rate
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