数控切割的钢材利用率要比手工切割的钢材利用率（）。
A.高10%~15%
B.相等
C.低10%~15%
D.低15%~20%
参考答案：C
The concert _______ many foreign students were invited was a feast for the eyes.
A．for which
B．to which
C．in which
D．on which
平地是指绝大部分地面坡度在（）以下。
A、2度
B、3度
C、5度
D、10度
