【今日情节】今天我们要学的词是 

pollution污染




　

【友情提示】只需听写文中出现的英文句子，今天有1个句子哟。^_^


Hints: 


One of the big problems in freeing the city from pollution is that its citizens are using cars more and more.
使城市不受污染的困难之一是城市居民越来越多地使用汽车了。