阅读下面短文，根据短文大意及图示，在每个空格上填上一个意义相符、形式正确的单词。

     The world is becoming much smaller ____ using modern traffic and modern communication. Life today is much easier than it was hundreds of years ago, ____ it has also brought new problems. One of the biggest ____ is pollution. To pollute means to make things dirty. Pollution comes in many ____.

     We see it, smell it, drink it, and even hear it.

     Man has been polluting the earth .The more people, the ____ pollution. Air pollution is the most serious. It's bad for all living things in the world, but it is not the only kind of pollution. Water pollution both kills fish ____ pollutes our drinking water. Noise pollution makes us angry more easily. Many countries are making rules in ____ to fight pollution. They stop people ____ burning coal in houses and factories in the city, and from putting dirty smoke into the air. Pollution ____ is caused by heavy traffic is now the most dangerous kind of air pollution. We are sure that if there are fewer people driving, there will be less air pollution. It's our duty to ____ the earth— our only home.