be going to do、be about to do、be to do,这三者有什么区别?从红框中,我也看不出到底有什么区别?三者的意思一样啊?

be going to do sth be going to do 后跟 be to do和be going to do的区别 be to do,be going to do,will do,be about to do的区别. be going to be going 英语be going to do还是doing 用be going to do造句 be going to do结构的用法 be going to do 的被动语态 be going to do 是什么时态? be going to do什么时态 be to do.be going to do.be doing.will do.有什么区别? be going to do/be doing/will do/be to do等 的区别~ be going to,be doing,will do有什么区别 be doing与be going to do有什么区别? will be 与be going to do 的用法 be going to,be to do,be about to do 有什么区别 be going to do的句式里是不是be going作谓语,to do作状语?