—What were you doing _____ it was raining?

—I was getting out of the library.[ ]

A. when                

B. if        

C. while            

D. as

含水层的导水系数T，可以反应（）。

A.含水层的透水能力 

B.含水层的厚度 

C.含水层的出水能力 

D.含水层通过水的能力