past perfect tense
She talked about the new job on the way to London and before long,I realized that she _15__ for my firm.I _16__ in the firm for nearly 20 years.Our boss was really a very strict man.My own secretary _17__ so I must be her new boss._18__ fair to her.
15) A had been working B will go to work C is going to work D was going to working
16) A had been working B have been working C worked D have worked
17) A was left B leaves C had left D have left
这道题的答案都是用的过去完成时,请问为什么不用现在完成时呢.如果说,15题用现在完成时表示他还是这家公司工作,但用过去完成时感觉好像已经不在这家公司工作了?