It's 5 days            we came here. Why shouldn't we start?

A．when

B．before

C．as

D．since

隧道洞内施工测量中，洞内散设路线应由洞口高程、控制点向洞内布设，结合洞内情况，测点高距以()为宜。

A．100～300m

B．100～400m

C．200～400m

D．200～500m