根据材料，回答题。 Sharks Perform. a Service for Earth"s Waters.It is hard to get people to

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

请帮忙给出正确答案和分析，谢谢！