There is a new problem in the popularity of private cars road conditions need to be improv

问题补充：

There is a new problem in the popularity of private cars road conditions need to be improved .

A. involving ; that

B. involved ; that

C. involved; where

D. involving ; which

答案：

A. involving ; that

(答案→)B. involved ; that

C. involved; where

D. involving ; which

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