If you said nimbostratus, you are correct.

如果你选云，你是正确的。

Water ice crystals interact with ammonia, which acts as a natural antifreeze, allowing liquid water to exist in the upper cloud layer.

水冰晶与氨发生相互作用，氨起到天然防冻剂的作用，使液态水能够存在于高云。

The beauty of Howard's system was that the basic components could be freely recombined to describe every shape and size of passing cloud--stratocumulus, cirrostratus, cumulocongestus, and so on.

霍华德体系的妙处在于，这些基本分可以自由组合，描述天空飘过的每种形状、每种大小的云——一积云、卷云、积云等等。

For instance, stratus clouds-those unlovable, featureless sprawls that give us our overcast skies, happen when moisture-bearing updrafts lack the oomph to break through a level of more stable air above, and instead spread out, like smoke hitting a ceiling.

比如，要是携带水汽的上升气流无法突破上面比较稳定的一空气，就会像烟碰到天花板那样向外展开，于是就形云一那种不大讨人喜欢，毫无特色，弄得天空阴沉沉的云。

There are five primary cloud types: stratus, cumulus, stratocumulus, cumulonimbus  and cirrus, each of which are subdivided into different genera based on altitude.

有五种主要的云类型：云、积云、积云、积云和卷云，每种云都根据海拔高度细分为不同的属。

Using the Stratocruiser fuselage resulted in the cargo compartment's floor being only 8 ft 9 in (2.7 m) wide.

使用云客机的机身导致货舱地板宽度仅为8英尺9英寸（2.7米）。

Howard believed that all clouds belonged to three distinct groups: cumulus, stratus and cirrus.

霍华德认为所有的云属于三个不同的类别：积云、云和卷云。

6000 meters, forming icy cirrostratus layers.

6000 米的水平云，形冰冷的卷。