Hundreds of years ago，life was much harder than it is today．People didn't have modern machines． However，life today has brought new problems．One of the biggest is （76）pollution．Water pollution makes our rivers and lakes dirty．It （77）kills our fish and pollutes our drinking water．Noise pollution makes （78）us talk louder and become angry more （79）easily．Air pollution is the most serious kind of pollution．It's bad for all the living things in the world． Many countries have made rules to fight pollution．Now factories must clean their water before it was thrown away，and they mustn't blow（吹）dirty smoke into the air．And if there are fewer people driving，there will be （80）less pollution．
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