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Why sharks are useful for humans.*
A．Their tasty meat.
B．The principle of their defense system against disease.
C．Their solid skin.
D．The principle of their birth modes.
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更多“Why sharks are useful for huma…”相关的问题
What is mainly described in Paragraph 2？
A．How and why sharks "hit and run".
B．How people can predict the attack.
C．How traditional prey is captured.
D．Why the human is a foreign object.
A．big heads
B．slender bodies
C．wide lobes
D．big fins
Why may the bull sharks attack people frequently？
A．Because human being is their favorite food.
B．Because they may wildly attack anything in the area.
C．Because they swims in shallow waters where people swim.
D．Because they are very aggressive sharks.
Why do sharks normally swim between ten and twenty miles off the coast of Britain？
A．They prefer warm water to cold water.
B．They see best in deep water.
C．They are afraid of man.
D．That is where their food is.
Why are sharks useful for humans？
A．For their tasty meat.
B．For the principle of their defense system against disease.
C．For their solid skin.
D．For the principle of their birth modes.
Why is the demand for shark fins rising in Asia？
A．Because there are fewer sharks in Asia.
B．Because shark fins can be used for medical purposes and for food.
C．Because shark fins are poisonous.
D．Because shark fins are expensive.
Why may the bull sharks attack people frequently？
A．Because they swims in shallow waters where people swim.
B．Because they may wildly attack anything in the sea.
C．Because human being is their favorite food.
D．Because they are very aggressive sharks.
It's a classic mystery of the deep. Why does the hammerhead shark (双髻鲨)have the bizarrely shaped head from which it gets its name？
There have been a variety of suggested explanations. Some simply say that the sharks use their heads to "hammer" and pin down their favourite food. More plausibly, others have speculated that the wide lobes(圆形突出部分)of the hammerhead allow it to have longer electrorecep-tots, the organs that all sharks use to detect the electric fields produced by nearby prey. This might allow hammerheads to sense subtler electric fields from more distant prey than their narrow-headed cousins.
Now it turns out that the shark's head does indeed help it find and capture prey, but not in the way that zoologists expected. Stephen Kajlura and Kim Holland of the University of Hawaii at Manoa set out to test the conventional theory by tricking young sharks into chasing phantom (虚构的)prey. Using a system of wires on the bottom of a shallow pool, they set up electric fields that mimicked those created by the bottom-dwelling shrimp and fish that form. the sharks' usual diet.
Sure enough, hungry sharks abruptly turned towards an electric field when they detected it. But when the researchers measured the distance at which this happened they found it was the same for 13 young hammerheads as it was for 12 young sandbar sharks(沙堤鲨),which have normal-shaped heads.
The two types of sharks proved equally adept at sensing the electric fields: each was able to detect the source from up to 30 centimetres away. That ruled out any improved sensitivity from the wider head. However, the hammerheads enjoy another more prosaic(平淡无奇的)advantage: their wider heads let them sweep more than twice as wide a swathe of the seafloor as they swim, which must boost their chance of encountering food.
The researchers also found that hammerheads could turn more sharply when they detected the phantom prey. "They're a much more bendy shark , "says Kajlura, who is now at the University of California at Irvine. In part, that's because they have more slender bodies than the sandbar sharks. However, Kajiura has other unpublished data that suggests that the hammerheads' broad heads can act as fins to improve manoeuvrability(机动性).
So far, the researchers have only experimented with young sharks, so adult hammerheads may gain some other advantage from their head shape.
The passage is mainly about ______.
A．the different species of sharks
B．the differences between hammerhead and sandbar sharks
C．how hammerhead sharks detect their prey
D．special functions of the hammerhead sharks
根据以下材料，回答题
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 smell4. It can find small amounts of substances in water， such as blood， body liquids and 59______ produced by animals. These powerful 60______ help sharks find 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.
回答（51）题 查看材料
A.attack
B.meet
C.love
D.visit
根据材料，回答题。
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 ________ （54） of disappearing from earth.
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 find 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 systems________ .（62） 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.
回答（51）题 查看材料
A.attack
B.meet
C.love
D.visit
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