一个新的研究表明它们飞得很快并全靠自己产生的气流，没有那预想中的上升气流帮它们提升到天空般的高度。
A new study shows that they do it quickly and under their own steam, without the help of upslope tailwinds thought to loft them over the sky-high peaks.
但最近，面对“顾客永远不需要付钱”的招牌时，我们对“免费”的痴迷又上升到了一个新的高度。
But recently, our obsession with free has given rise to a new phenomenon - where the customer is never asked to pay.
不仅没有给未来一个光明的前景，反而扩大了现有的分歧，把美国国内的愤怒与恐惧上升到了一个新的高度。
Instead of painting a bright vision for a unified future, he magnified the divisions of the present, inspiring new levels of anger and fear within his country.
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