Convenient private cars are for us, they may also cause traffic accidents and pollution.
A. while
B. as
C. if
D. since
网友回答
A. while
(答案→)B. as
C. if
D. since
解析：考查让步状语从句。形容词/名词/动词+as +主语+谓语，意为“尽管......”。句意“尽管私家车对我们来说很方便，但它们也可能引起交通事故或污染。”本题是让步状语从句。While也用“尽管”的意思，但while引导一个完整的句子。故选B。