1)　shall用于第一人称，常被will 所代替。
        will 在陈述句中用于各人称，在争求意见时常用于第二人称。
        Which paragraph shall I read first.
        Will you be at home at seven this evening?
        
        2)　be going to +不定式，表示将来。
        　 a. 主语的意图，即将做某事。
        　What are you going to do tomorrow?
        　 b. 计划，安排要发生的事。
         The play is going to be produced next month。
        　 c. 有迹象要发生的事
         Look at the dark clouds, there is going to be a storm.
        
        3)　 be +不定式表将来，按计划或正式安排将发生的事。
         We are to discuss the report next Saturday.
        
        4)　be about to +不定式，意为马上做某事。
        He is about to leave for Beijing.
        　 注意：be about to 不能与tomorrow, next week 等表示明确将来时的时间状语连用。