程控交换机计费是在用户()开始的。
A、摘机
B、听回铃音
C、听拨号音
D、应答时
参考答案:D
— Just now Jenny gave ten dollars to a person in trouble.
— She________others. [ ]
A. was always helping
B. is always helping
C. always helped
D. had always helped
振动测试作业时夹具未卡紧可能导致的事故及违章行为级别是什么?