—Do you know where the headmaster is? I have something urgent.　　　　—Oh, he ____ have gone far, for the computer is still on in the office.

---You _________to our Mom like that. It was awfully impolite. ---You are right. I must have been crazy at that moment.

Generally speaking, my grandmother is nice and kind, but she _______ be very stubborn at times.

_______ he had not hurt his leg, John would have won the race.

In order to do something meaningful, it’s necessary that you _______ determine what is really important.