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 seemed to be【A1】_____.

Today things are【A2】_____, the world has become too【A3】_____. We are using up our natural resources too quickly and at the same time we are【A4】 _____ our environment with dangerous chemicals. If we continue to do this, human life on the earth 【A5】_____ survive.

Everyone 【A6】_____ today that if too many fishes are taken from the sea, there will soon be none left. Yet, with modern fishing【A7】_____ more and more fishes are caught. We know that if too many trees are cut down, 【A8】_____ will disappear and nothing will grow on the earth. Yet we【A9】_____ to use bigger and more powerful machines to【A10】 _____ more and more trees.

We realize that if rivers are polluted with waste products from factories, fish will die.【A11】_____in most countries wastes are 【A12】_____ put into rivers or into the sea, and there are【A13】_____ laws to stop this.

We know, too, that if the【A14】_____ of the world continues to rise at the present rate, in a few years there will not be enough 【A15】_____. What can we do to solve these problems?

If we eat more vegetables and less【A16】_____, there will be more food available for everyone. Land that is used to grow crops【A17】_____ five times more people than land where animals are kept. Our natural resources will【A18】_____ longer if we learn to recycle them.

The world population will not rise so quickly if people use modern methods of birth【A19】_____. Finally, if we educate people to think about the problems, we shall have a better and cleaner【A20】_____ in the future.