A-A+
A．they do not land thereB．there are not clouds
问题详情
A．they do not land there
B．there are not clouds at all
C．they can cross the ice with special equipment
D．it is very cold
参考答案
正确答案：B
解析：综合理解题。在北极上空，飞机通常不需要迅速爬高或上升，因为在那一高度，根本就没有云层，同时冷空气也会使云层下落降低，所以B项正确。
