Hydrogen is a useful gas for balloons. It is lighter than air.

氢气对于气球来说是一种有用的气体，它比空气轻多了。

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I'll refill my cigarette lighter with gas.

我将给打火机再灌满汽油。

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I'll refill my cigarette lighter with gas.

我将给打火机再灌满汽油。

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