1970 was World Conservation Year.The Unite Nations wanted everyone to know that the world is in danger.They hoped that governments would act quickly in order to“conserve”nature.Here is one example of the problem.At one time there were 1 000 different plants，trees and flowers in Holland，but now only 860 remain.The others have been destroyed by modern man and his technology.We are changing the earth，the air and water，and everything that grows and loves.We can’t live without these things.If we continue like this，we shall destroy ourselves.
What will happen in the future? Perhaps it is more important to ask，“What must we do now?”The people who will be living in the world of tomorrow are the young of today.A lot of them know that conservation is necessary.Many are hoping to save our world.They plant trees，build bridges across rivers in forests，and so on.In a small town in the United States a large group of girls cleaned the banks of 11 kilometers last Sundays in order to protect their surroundings.“No one’s going to change our world”is popular with others.It was made by the Scathes Cliff Richard and other singers.The money from it will help to conserve wild animals.
46.There are fewer plants，trees and flowers in Holland now because_______.
A.there has been a lot of conservation in Holland
B.Holland does not need so many plants，trees and flowers
C.many plants，trees and flowers can not grow there any more
D.some plants，trees and flowers are dangerous
47.We shall destroy ourselves if we don’t change_______.
A.the United Nations B.modern technology
C.our rivers and forests D.the government
48.“No one’s going to change our world”was_______.
A.an important book published in 1970
B.an idea that nobody would accept
C.a record calling on people to conserve nature
D.a ruler worked out by the United Nations
49.What is the most important thing for us to do to save our world?
A.We should plant more trees and flowers.
B.We should know what will happen in the future.
C.We should know it is necessary to conserve nature.
D.We should know what we must do and begin to do it now.
50.What’s the main idea of the passage?
A.1970 was the World Conservation Year.
B.Conservation is necessary.
C.It is the young people who are helping to save our world.
D.The United Nations wanted everyone to know that the world is in danger.