—Who______ it be that is knocking at the door?—It ______ be Father, but I’m not sure.
I regret _____ hard at school, or I would have succeeded in passing the exam.
We should prevent such a silly mistake _____ again.
_____ full preparations, we decided to put off the meeting till next week.
I’m examining the article he has just finished _____ the possible mistakes in it.
How could he get the plan _____ without any one to support him?