常规单模光纤的零色散波长窗口在（）
A、0.85µm
B、1.31µm
C、1.55µm
参考答案：B
(2013·辽宁高考)At no time ________ the rules of the game. It was unfair to punish them.
A．they actually broke
B．do they actually break
C．did they actually break
D．they had actually broken
锅炉装向空排汽门的目的，只是作为锅炉蒸汽压力高时排汽用的阀门。（）
