操作钻机在合立轴时，应在（）进行。
A.待齿轮停止转动后
B.齿轮转速最快时
C.齿轮转速较慢时
D.齿轮转速正常时
参考答案：A
Nearly two weeks passed_____the old man was able to explain what had happened to him.
A．when
B．till
C．before
D．while
铁路局应设专人负责长大货物车的（）、检修工作。
A.运用
B.管理
C.装卸
D.运输
