There is another way to survive this competition-a way no one ever seems to tell you about, ________

you have to learn for yourself.[ ]

A. it  

B. that

C. one  

D. another

不属于隧道围岩分级考虑的因素是（）。

A.岩石的坚硬程度 

B.岩体的完整程度 

C.岩石节理的发育程度 

D.地下水的影响