Finally, it was Robert Plath, who was an airline pilot, who invented a new, wheeled suitcase, which he patented in 1991.

后来一个叫罗伯特·普拉斯的飞行员，发明了一种滚轮行李箱，并且在1991年取得专利权。

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It turns out to be-- there's a fairly complicated balance between the time of flight and the range.

答案表明,在飞行时间与射程之间,有着一个相当复杂的平衡关系

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