带式输送机要求打滑检测装置什么情况下出事故信号?
参考答案:
要求打滑检测装置在带式输送机的运行速度底于正常运行速度的75%或高于110%时发出事故信号。
There is a new problem involved in the popularity of private cars _______ road conditions need _______.
A.that; to be improved
B.which; to be improved
C.where; improving
D.when; improving
把一个直径为10厘米粗的实心钢管锯断1次要用5分钟,锯断3次需要( )分钟。