pleace they must have finished their work by now.为什么用have fi
pleace they must have finished their work by now.为什么用have finished?
they finally succeeded in carrying out the experiment.
they must have finished their work by now.为什么用have finished?
i have been looking forward to hearing from you.为什么用have been?
it has not been decided yet when the meeting will start at the hall.为什么用been,不要be?
i won't visit that restaurant today.won't 在什么时候用?