名词
中文翻译：气囊
同义词：
['gas sacs', 'air sacs', "gas cavities例句：1. The bird's air sacs are filled with air", 'which helps it fly.（这只鸟的气囊充满了空气，这帮助它飞行。）']
例句：
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1. The bird's air sacs are filled with air, which helps it fly.
这只鸟的气囊充满了空气，这帮助它飞行。
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2. The scientist discovered that the air sacs in the lungs of mammals are filled with a mixture of oxygen and carbon dioxide.
科学家发现哺乳动物肺部的气囊中充满了氧气和二氧化碳的混合物。
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3. During flight, the air sacs expand to increase the bird's lift-off speed.
在飞行过程中，气囊会膨胀以提高鸟类的起飞速度。