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

A．that, to be improved

B．which, to be improved

C．where, improving

D．when, improving

管理跨度与管理层次的正确关系是（）。

A．层次减少跨度不变

B．层次越多跨度越小

C．层次越少跨度越小

D．层次越大跨度越大