下面哪一项是HFC网络反向调试的要点（）。
A、调整光发射机输出电平
B、光工作站AGC设置
C、调整前端设备上行接收电平
D、以上都是
参考答案：C
＿＿many times, he still didn’t make sense of it.
A．Having been told
B．Then he was told
C．Being told
D．He was told
利用分析
