PON系统采用单纤双向技术，上下行信号采用信号波长为（）A.上行1

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问题单项选择题

PON系统采用单纤双向技术，上下行信号采用信号波长为（）

A.上行1490nm/下行1310nm

B.上行1310nm/下行1490nm

C.上行1550nm/下行1310nm

D.上行1310nm/下行1550nm

答案

参考答案：B

选择题

The prices of the apartments downtown were _____ high so we ______ gave up the idea of buying one there and chose to live in the suburb.

A．constantly; approximately

B．generously; purposefully

C．extremely; eventually

D．frequently; unfortunately

多项选择题

穿山甲可用于治疗（）。

A.风湿痹痛

B.产后乳汁不下

C.癓瘕、经闭

D.痈肿疮毒、瘰疬

E.血淋、尿血