We find______ necessary to protect the earth．

A．it                  B．this                C．that                D．what

完形填空

　　1970 was World Conservation(保护) Year. Everyone must know that the world is in danger. 1 is one example of the 2 . At one time there were 1300 different kinds of trees and flowers in Holland(荷兰), but now only 866 remains(继续存在). 3 have been destroyed by modem man. We are changing the earth, the air and the water, and 4 that grows and lives. If we go on like this, we shall destroy ourselves.

　　What will happen in the future? Perhaps 5 is more important to ask“What must we do now?”The people who will be living in the world tomorrow are 6 young of today. A lot of them know that conservation is necessary. Many are helping to save 7 .

　　Now fifteen million young people in many countries are studying 8 and the country around him. In some countries they spend much time as“Conservation Volunteers(志愿者).”They plant trees and help to 9 wild birds and animals.

　　But everyone, 10 young people, must work to save our world.

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