实行郡县与王国并行的双轨管理体制的朝代是( )
A．秦朝
B．汉朝
C．唐朝
D．宋朝
参考答案：B
The traffic slowed down because of the heavy snow in Yushu county, presenting a new __________ to the recovery from the earthquake.
A．suffering
B．disaster
C．challenge
D．damage
安稳主站、子站和执行站之间的全程专线通道的传输电路时延要求？
