2.5G无FEC波分系统中，对OSNR的最低要求为（）。
A.18
B.20
C.22
D.24
参考答案：B
Monkeys in the zoo have shown the flu ______ since last Monday and altogether 20 have died until now. [ ]
A. symbol
B. sign
C. signal
D. symptom
大偏心受拉对称配筋时（）。
A.受压钢筋一定不屈服
B.受拉钢筋一定不屈服
C.受压区高度一定不小于2as’
D.受压钢筋一定不屈服和受压区高度一定小于2as’
