一道关于完成时的选择题

题目

一道关于完成时的选择题
why are you still working on this project?It's 4 o'clock in the afternoon and you're supposed ____ it by noon.
A.to finish
B.to be finishing
C.to have finished
D.to have been finishing
A怎么不行啊?有必要做完成时吗?
我总是分不清

答案

他们说的都不清楚.BE SUPPOSED TO DO STH 表示应该做某事YOU ARE SUPPOSED TO COME AT NINE.DONT BE LATE.BE SUPPOSED TO HAVE DONE STH表示应该做而没有做(有责备的意思)YOU ARE SUPPOSED TO HAVE COME AT NINE.WHY...