每次接通起动机应不超过（）秒钟，两次起动之间的间隔应在（）秒钟以上。
参考答案：5；15
He doesn't tell me when he _____. I'll call you up as soon as he _____. [ ]
A. will come, arrives
B. comes, arrives
C. will come, will arrive
一个以太网的帧数据长度为20字节，那么它的填充域长度是( )。
A．0字节
B．23字节
C．45字节
D．26字节
