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How big a problem is the pollution caused by cities?
城市造成的污染是个多么严重的问题？
youdao
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The pollution caused by autos is the most important problem at present.
由汽车造成的污染是目前最重要的问题。
youdao
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The pollution caused by autos is the most important problem at present.
由汽车造成的污染是目前最重要的问题。
youdao