the serious air pollution has done severe harm to people's health这里的has done怎么理解

why air pollution is the most serious? Air _____ (pollute) is the most serious of all. increasing serious problem,air The air was polluted by the gas from the factoties.The p_____ was serious the new flat rate poll taxes More and more people are worried about the serious air pollution 这个句子是什么时态 The harmful gas from the factories pollutes th air.The harmful gas from fact同义句转换The harmful gas from the factories pollutes th air.=The harmful gas from factories () the air ().This pollutes the Earth and kills animals an plants.=This poll 1.Air p_____is a serious problem in the world now.2.People will have m____free time in the future we were only three p（） in the city ten years ago and the air pollutionwas very serious we were only three p in the city ten years ago and the air pollutionwas very serious 根据句意及首字母或汉语提示完成单词 The big cities,air p____is quite serious. the air is polluted and our health is getting ___,worse and worse.A seriously B serious the serious air pollution has done severe harm to people's health这里的has done怎么理解 连词成句:girl,in,who,the,poll,is,swimming There is don't water in the poll. .He lived at the foot of South Hill and ___________ the fresh air.(breath) 8.He is ____________(serious)ill today.He stays at home. Air pollution is now a serious problem in China 英译汉 Air pollution is more serious than water pollution.的意思?