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Balloons are aerostats, which means that are lighter than air when inflated.
气球是轻飞行器,也就是说,充气后, 它们会比空气轻.
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Incendiary ammunition had been developed for use against observation balloons in France.
在法国,已经研究出用燃烧弹对付侦察气球的办法.
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They also discovered that the helium in the balloons would last for six hours.
他们也发现汽球中的氦气有效时限可达六小时.
常春藤生活英语杂志-2006年3月号
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The files blame other UFO sightings on weather balloons, clouds or normal aircraft.
有一些文件把其它的UFO目击事件归因为气象探测气球 、 云彩或正常的飞行器.
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