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。
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.__1__ Sharks eat fish, other sharks, and plants that live in the
ocean.
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, overfishing 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 become too great.__3__
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.__4__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.__5__
A. Shark liver oil is a popular source of Vitamin A.
B. This protects the plants and other forms of life that exist in the oceans.
C. Sharks are valuable to us and we can make full use of them.
D. 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. They are a threat to other forms of life in the ocean.
G. The others give birth to live young.