―Do you know where David is? I couldn’t find him anywhere.―Well. He ______ have gone far — his coat’s still here.

With the help of the smart phones, you ____ video chat with your friends on the phone.

We can eat in the dining hall. But we _______ eat in the classroom.

–Look at that girl! Is it Susan? --No, it _______ be her. She has gone back to her hometown.

— I regret to say that I          have shouted at you the other day．— Forget it． I was a bit out of control myself．