问答题

In practice, this is an advantage to the aeroplane, which is already at a good height when it reaches the polar region and so does not to climb, while at the same time cold air keeps the clouds down low. (Passage 1 )

【参考答案】

实践中,这对飞机有利,因为当它到达北极时不用爬升就已经处于一个很好的高度了,同时,冷空气也使云层降低。