如果采空区距（）也可从地表向釆空区打钻孔进行抽放
A.地表不深时
B.地表较深时
C.地表有裂隙时
参考答案：A
_____ the night, we did nothing but _____ there, waiting for him to come.
A．All through; sit
B．All over; to sit
C．Whole; sitting
D．Throughout; sat
NA代表阿伏加德罗常数，下列叙述错误的是（）。
A.选项A
B.选项B
C.选项C
D.选项D
