水准测量观测高差的中误差与线路长度s平方根成（）。
A.正比
B.反比
C.相等
D.无关
参考答案：C
For a long time, he hesitated whether he should tell us ____ what had happened.
A．at dusk
B．at length
C．at present
D．at stake
既能固精缩尿，又能明目的药物是( )
A．金樱子B．覆盆子C．桑螵蛸D．鸡内金E．海螵蛸
