计算一个氢气球的重量。

Try to measure a hydrogen balloon's weight.

牵一个氢气球代替游泳圈在海里游泳。

Hold a hydrogen balloon instead of a swim ring in the sea.

这对在生日派对上想要氢气球的孩子们可真不是个好消息！

Too bad for the kids who want hydrogen balloons for their birthday parties!