Sharks have been around for a very long time. It means that they have been on earth for thousands of years, and have changed little. A shark is a fish, but it has many {#blank#}1{#/blank#} from a fish. For example, if a shark {#blank#}2{#/blank#} swimming, it will sink(下沉).

    There are {#blank#}3{#/blank#} 200 and 250 kinds of sharks in different size. The largest can be {#blank#}4{#/blank#} long as 15 meters. Sharks feed on fish, {#blank#}5{#/blank#} sea animals, or smaller sharks. It is said that one of the most {#blank#}6{#/blank#} sharks is the Great White Shark. They have attacked(攻击) a number of people off the beaches of America. Australia, New Zealand and South Africa also have shark 0attacks. In some places there {#blank#}7{#/blank#}watchtowers on the beach to warn people about sharks in the water. {#blank#}8{#/blank#} a shark appears, a bell rings to tell people to get out of the water. Shark attack about 100 people a year in America. Perhaps the shark {#blank#}9{#/blank#}thinks that the people is a kind of sea animal, or {#blank#}10{#/blank#} good to eat.

    One day, a student asked his teacher, "what is greed?" The teacher didn't answer his question{#blank#}1{#/blank#} , but asked the student to walk through the chocolate factory next to their school and pick out the biggest chocolate bar（条、块） he could find．But there was a {#blank#}2{#/blank#}: as he passed through the factory, he could not turn back.

    The student went to the chocolate factory. As he walked, he saw a large chocolate bar. He liked it, but thought he might be able to find an even bigger one if he kept going. He kept walking and saw {#blank#}3{#/blank#} chocolate bar. This one was a little bigger. But {#blank#}4{#/blank#}, he thought he could find an even bigger one if he kept going. As he neared the end of the factory, he saw fewer chocolate bars, and {#blank#}5{#/blank#} of them were as large as the earlier ones. He started to regret his decision to keep going. Finally, he {#blank#}6{#/blank#}. He went back to his teacher empty-handed and explained what had happened.

    The teacher told him, "You liked the {#blank#}7{#/blank#}chocolate bar, but you kept looking for a bigger one. And later, you realized that you had given up the best chocolate bar because you thought you could do better. That is called greed."