Question

Susan _______out _______the door opened and in came three strangers.

1. A.
   was just to go; while
2. B.
   just went; as
3. C.
   was just going; as soon as
4. D.
   was just about to go; when

Answer 1

D
be about to do sth. when是一個固定的句型，表示正要做某事的時候突然發生另外一件事。when此處相當于并列連詞，意為“on the point of doing sth.”,“be going to do sth.”等。