题目内容：

根据短文内容，从短文后的选项中选出能填入空白处的最佳选项，选项中有两项为多余选项。（如果所用的答题卡没有E、F、G选项，则选E涂A、B，选F涂A、C，选G涂A、D。）

Sharks have lived in the world’s oceans for millions of years. A shark has a very good sense of smell. It can find small amounts of substances in water, such as blood, body liquids and chemicals produced by animals. These powerful senses help sharks find their food.    1.

Sharks grow slowly. About forty percent of all sharks lay eggs.    2.   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.

3.   They eat injured and diseased fish. Their hunting activities mean that the numbers of other fish in ocean waters do not become too great. This protects the plants and other forms of life that exist in the oceans.

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.   4.   Shark liver oil is a popular source of Vitamin. 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.    5.  If too many sharks in one area are killed, the group of sharks may never return to normal population levels.

A. The others give birth to their young.

B. Sharks are important for the world’s oceans.

C. This is a threat to other forms of life in the ocean.

D. Collectors pay thousands of dollars for the jaws of a shark.

E. Sharks are valuable to us and we can make full use of them.

F. But some sharks are in danger of disappearing from Earth.

G. Sharks eat fish, other sharks, and plants that live in the ocean.