be to do sth.与will do /be doing 的区别

Question

如题所述

Answer 1

be to do sth -----强调已经决定并且不会改变：
1 Tom is to go there next Monday.
2 If you are to pass the exam, you have got to work hard.

will do-------往往强调到了时间事情就会发生：
Our bus will start in 10 minutes, at 3:00 o'clock. (只要在3:00,就会出发)

will be doing-----强调某件事情在将来某个特定时间就会发生
1 Our bus will be leaving for our destination at 3:00 for sure.
2 This time tomorrow, Mr. Smith will be taking a nap in his car by the roadside.

Answer 2

除了上述知友回答的区别外，两者还有一个区别：
be to do sth一般表示客观的要发生什么事情。而will do \ doing 主要表示个人主观上将要做什么。

Answer 3

be to do表示“计划”或“安排好的事项”。例如：
Betty is to be married soon
The children are to learn English next Monday
will do表示将要发生的动作或临时起意
1.They will leave for Shanghai tomorrow.
2.He will be back in a few days.

现在进行时用来表示将要发生的动作，多与表示位置移动的动词 come，go，leave，fly ，start 等连用。
He is leaving for London