It must be going to rain tomorrow,isn't it?还是 won't it
问题描述：
It must be going to rain tomorrow,isn't it?还是 won't it
答
毫无疑问应该是--isn't it?
反意疑问句的疑问部分引导词与将陈述部分变为一般疑问句时所用引导词保持一致,我觉得在mustn't it和isn't it?之间犹豫更加可以理解一些.如果换成前者就是明天必须要下雨了,非常不通顺.