检修设备时，不锁定或多人作业只挂1把安全锁（）
参考答案：错
激活补体活化的经典途径中必不可少的补体成分是()
A．C1
B．C2
C．C3
D．C4
E．C6
— What's the time?
— It's ________________. [ ]
A. half past six
B. sixth o'clock
C. sixth
D. the sixth
