Air pollution is getting more and more serious in many places around the world．The fact that public parks in cities become crowded proves that people long to breathe in green，open spaces．And，in these surroundings，they are generally both peaceful and peaceable．It is rare to see people being at odds or even fighting in a garden．It seems to be proved that if human beings can freely breathe and share air，there is no primary reason for them to struggle with one another．

But do we only sense what life could be when we enjoy green spaces？

Theplant worldsilentlyshowsuswhat areflectionoflifetruthfullyis．Italsohelpsustoanewbeginning，urgingustocareforourbreath．Wemust，inturn，careforit，opposinganysort of pollution that destroys both our world and that of plants．The interdependence to which we must pay the closest attention is what exists between ourselves and the plant world．Often described as"the lungs of the planet"，the woods that cover the earth offer us the gift of breathable air by releasing oxygen．But their capacity to renew the air polluted by industry has long reached its limit．If we continue to pollute the air by filling it with chemicals and destroy the ability of plants to restore it we will soon pull our world into an unavoidable disaster．

Humans must learn to share life，both with each other and with plants．This task can be carried out only when each takes it upon her 一 or himself 一 and only when all work together．The lesson taught by plants is that human life can only exist with nature．We must come to view the air，the plants and ourselves as the contributors to the protection of life and growth，rather than productive objects we can use and throw away freely．Perhaps then we would finally begin to live，rather than merely survive．

51．What does the underlined part"being at odds"mean？___

A．relaxing B．exercising C．hurrying D．conflicting

52．According to the first paragraph，what does th