有一读者问： 有这样一道选择题：
(1)He was_________when I walked into the room.
A. ready for leaving B. about to leave
C. on the point of leaving D. already to leave
答案为B，其他几个答案为什么不行？
之所以应选B是因为其后有一when（有“突然”或“意外”的内涵）从句的缘故。这是一种惯用搭配，再如：
(2)She was about to leave when Mark arrived so she stayed a little longer.
