EPON无源光网络由以下那几部分组成:()
A.OLT
B.ODN
C.ONU
D.DWDM
参考答案:A, B, C
—Tom!Look at the man in black over there.Can you tell me ________?
—Oh!He is my friend,Jim.
A.what he is B.who he is C.how he is
管道的的磨损和堵塞正常的解决方法是()。
A.定期检查管路的磨损情况
B.定期翻转管道
C.在泵的入口处加装滤网
D.及时更换
E.及时处理水龙头处杂物