在运输布局的基本方法“最小生长树规划法”中，第四阶段是按各路段（）和紧密程度，形成了网内主通道。

A.运输干线长度

B.网内线路密度

C.交通流量的大小

D.网内货流强度

--- I hear there was a road accident this morning.

--- Yes. __________ car hit the blocks and __________ driver was badly injured.

A．/; /

B．The; a

C．The; the

D．A; the