In the past, man did not have to think about the protection of his environment.  There were few people on the earth,  and natural resources（资源） seemed to be    26  .
Today things are 27 , the world has become too   28   . We are using up our natural resources too quickly, and at the same time we are  29  our environment with dangerous chemicals. If we continue to do this,  human life on the earth will not   30  .
Everyone 31  today that if too many fish are taken from the sea, there will soon be none left.  Yet, with modern fishing  32   , more and more fish are caught.  We know that if too many trees are cut down,  33 will disappear and nothing will grow on the land. Yet, we  34  to use bigger and more powerful machines to 35  more and more trees.
We realize that if rivers are polluted with waste products from factories, we will die. ___36,    in most countries wastes are 37   put into rivers or into the sea, and there are 38   laws to stop this. We know, too, that if the   39  of the world continues to rise at the present rate, in a few years there will not be enough food. What can we do to  40  these problems ?
If we eat more vegetables and less   41 , there will be more food available for everyone.  Land that is used to grow crops   42  five times more people than land where animals are kept.  Our natural resources will  43  longer if we learn to recycle them.  The world population will not rise so quickly if people use modern methods of birth 44    .
Finally, if we educate people to think about the problems, we shall have a better and cleaner     45   in the future.

A．beautiful B．unlimited C．rare D．valuable

A．common B．the same C．changeable D．different

A．crowded B．small C．dirty D．busy

A．protecting B．saving C．polluting D．fighting

A．breathe B．survive C．drink D．move

A．wonders B．realizes C．considers D．discovers

A．poles B．boats C．methods D．ideas

A．mountains B．the sea C．trees D．forests

A．continue B．stop C．keep D．go on

A．grow B．plant C．save D．cut down

A．Thus B．However C．But D．Therefore

A．still B．even C．also D．certainly

A．too many B．a few C．some D．few

A．production B．pollution C．population D．pronunciation

A．work B．deal C．solve D．serve

A．fruit B．meat C．fish D．grain

A．feeds B．increases C．supplies D．helps

A．use B．stay C．keep D．last

A．control B．born C．plan D．reward

A．nature B．sea C．planet D．forest