The most important sources请帮忙翻译下

问题描述:

The most important sources请帮忙翻译下
The most important sources of air pollution in China are the emissions of().
1.plane 2.motorcycles.3.Auto 4.industrial emissions

中国最重要的空气污染来源是什么的排放
1、飞机2、摩托车3、汽车4、工业排放
3或4?