救生衣衣身以及每一圈提环应能承受3200N的作用力（）而不损坏。
A.15min
B.30min
C.45min
D.60min
参考答案：B
Children in the country should have the right to ask for ______education opportunities as those in the city.[ ]
A．equal
B．unfair
C．common
D．usual
在机场区域内，仪表飞行航空器距离障碍物最高点的最低垂直间隔，丘陵和山区不得小于（）米。
A.300
B.400
C.500
D.600
