Sharks are among the oldest animals on Earth. There are hundreds of kinds of sharks. Most are about two meters long. The dogfish shark, however, is less than twenty centimeters in length. A shark has an extremely good sense of smell. It can find small amounts of substances in water, such as blood, body liquids and chemicals produced by animals. 71 Sharks eat fish, other sharks, and plants that live in the ocean.
Sharks grow slowly. About forty percent of all sharks lay eggs. 72 Some sharks carry their young inside their bodies as humans do. Some sharks are not able to reproduce until they are twenty years old．Most reproduce only every two years. And they give birth to fewer than ten young sharks. For this reason, over-fishing of sharks is of special danger to the future of the animal.
Sharks are important for the world’s oceans. They eat injured and diseased fish. Their hunting activities mean that the numbers of other fish in ocean waters do not bee too great. 73.
People hunt sharks for sport, food, medicine and their skin. Experts say the international market for some kinds of sharks has increased because many parts of a shark are valuable.
Collectors pay thousands of dollars for the jaws of a shark. 74 The skin of a shark can be used like leather.
In Asia, people enjoy a kind of soup made from shark fins. Experts say a fisherman can earn a lot of money for even one kilogram of shark fins. Sharks are among the oldest animals on Earth, but some sharks are in danger of disappearing from Earth.75.A．Shark liver oil is a popular source of Vitamin AB．This protects the plants and other forms of life that exist in the oceansC．Sharks are valuable to us and we can make full use of themD．These powerful senses help sharks find their food E．If too many sharks in one area are killed, that group of sharks may never return to normal population levels
F． his is a threat to other forms of life in the ocean.
G．The others give birth to live youngD
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(答案→)D
解析：本文主要介绍了有关鲨鱼的一些情况。鲨鱼的嗅觉很灵敏，鲨鱼哺育孩子的方法，鲨鱼对于海洋的重要性，人们为了利益捕杀鲨鱼，鲨鱼的现状很危险。
【小题1】D 前面提到了鲨鱼的嗅觉很好，下文有提到了鲨鱼的一些事物。故此处应是与“鲨鱼的嗅觉帮助它寻找食物”有关的 D这些强烈的嗅觉帮助鲨鱼寻找他们的食物。 故选D
【小题2】G 前文提到了40%的鲨鱼产卵，下文提到了一些鲨鱼像人类一样在体内哺育孩子。故此处应是与“生产”有关 G 其他的是胎生。 故选G
【小题3】B 前文提到了鲨鱼在海洋中很重要，它吃掉受伤和有病的鱼，这维持着海洋生物链的平衡。 所以应是与“保护海洋里的一些生物“有关的 B这保护了海洋里的植物和其他鱼类的存在。
【小题4】A 下文提到了鲨鱼的皮肤能当皮革，上文提到了收集者花上千美元买鲨鱼的颌骨。所以此处应填鲨鱼的某处的作用 A鲨鱼肝石油是一种流行的来源维生素 故选A
【小题5】E 前文提到了鲨鱼处于危险的地步。所以此处应是鲨鱼被杀的后果。
E如果太多的鲨鱼在一个地区被杀害，这一群的鲨鱼可能永远不会返回到正常的人口水平
故选E