[单选] 完型填空 51-60 题（每小题 2分，共 20分） Life today is much 1 than it was hundreds of years ago， but it has brought some 52 problems． One of the biggest problems is pollution． We can see it， smell it， drink it and even 53 it． Man has polluted the earth． The more people， the more pollution． Many years ago， the problem was not so serious because there were not so 54 people． When the lands were used up or the rivers were not clean in a place， man went to another place． Man is now slowly 55 the whole world． Air pollution is still the most serious． It’s bad for all living things in the 56 ， but it is not the only one kind of pollution． 57 pollution kills our fish and pollutes our drinking water． Noise pollution makes us 58 more easily． Many countries are making rules to fight pollution． They stop factories from pouring dirty water into rivers and putting dirty 59 into the air． Except for this， we can do many more things． For example， if there are fewer people driving， there will be 60 pollution， too． The earth is our home． We must take care of it．