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

There is a new problem involved in the popularity of private cars road conditions need to be improved.
A. that
B. which
C. where
D. when

(答案→)A. that B. which C. where D. when解析：该句为分隔性同位语从句。that引导同位语从句，作problem的同位语，解释problem的具体内容。

和我的回答一样，看来我也对了