cloud是可数名词还是不可数名词?广泛寻求答案．

1. 云[C][U]
The sky became suddenly covered with dark clouds.
天空突然变得乌云密布.
2. (尘埃、烟等)云状物[C][(+of)]
3. (移动中的昆虫、鸟等的)一大群[C][(+of)]
A cloud of locusts hit the farm.
大群蝗虫袭击了那个农场.
4. 阴影;阴云[C]
5. (大理石等的)黑斑[C]
[C]可数
[U]不可数