11.5 be going to / will ， be to和be going to

11.5 be going to / will 用于条件句时，be going to表将来,will表意愿。例如：

　　If you are going to make a journey, you'd better get ready for it as soon as possible.

　　Now if you will take off your clothes, we will fit the new clothes on you in front of the mirror.

be to和be going to 

　　 be to 表示客观安排或受人指示而做某事，be going to 表示主观的打算或计划。例如：

　   I am to play football tomorrow afternoon.　　明天下午我去踢球。（客观安排）

　   I'm going to play football tomorrow afternoon.  明天下午我想去踢球。（主观安排）