hot-air ballooning短语¹¹⁴⁴⁶⁷⁺⁴ 基本例句 网乘热气球；乘坐热气球；热气球观光20世纪80年代澳大利亚兴起的热气球旅游 An atmosphere composed of a cold gas mix that is lighter than helium and not much heavier than hydrogen, means that hot-air ballooning will need to be used. 一个由寒冷气体混合比氦要轻但是不会比氢重很多的大气层，意味着热气球将需要使用。 yeeyan