Question

―The telephone is ringing.
   ―I _________ answer it.
 A. will                 B. am going to
C. am to               D. am about to

Answer 1

A

 

be going to do表示“已计划好要做某事”，be to do与be about to do有时意思一样，都是“正要做某事 (忽然另一个动作发生了)”。