be supposed to be doing到底要怎么用?比如说：I'm supposed to be doing my homewoek为什么不是I'm supposed to do my homeworkwe are supposed to be useing this book为什么不是we are supposed to ues this book.这里的suppose to do是指

be supposed to be doing到底要怎么用?比如说：I'm supposed to be doing my homewoek为什么不是I'm supposed to do my homeworkwe are supposed to be useing this book为什么不是we are supposed to ues this book.这里的suppose to do是指
be supposed to be doing到底要怎么用?
比如说：
I'm supposed to be doing my homewoek
为什么不是
I'm supposed to do my homework
we are supposed to be useing this book
为什么不是
we are supposed to ues this book.
这里的suppose to do是指应该的意思.

be supposed to be doing到底要怎么用?比如说：I'm supposed to be doing my homewoek为什么不是I'm supposed to do my homeworkwe are supposed to be useing this book为什么不是we are supposed to ues this book.这里的suppose to do是指
一个是被期望做什么(应该做),一个是被期望(在某时间)正在做什么(应该在做).如果没有特殊要求,你的两组句子都是对的.