Look at these black clouds,
问题描述：
Look at these black clouds,
It'll rain 还是 It's going to rain?
答
It'll rain.
be going to 表将来,是说按计划安排好的.
下雨不是安排好的,用will.答案是 It's going to rain为什么？sorry,错了，的确是用be going to这里是be going to +动原的另外一个用法用来表达某种迹象，表明要发生的事。条件句说明了下雨的前兆，所以是用来表明一种迹象的发生。