We all know that we ________ our carbon footprint, but I suspect that many people wouldn't be prepared to go as far as Joan Pick, a retired scientist living in south London.

—I didn’t tell him the news.—Oh, you ought _______.

— Bill, is the pink umbrella Anna’s?— No, it _____ be hers. Hers is purple. 

Five-star hotels provide better services than some small hotels. You _______ even use free WIFI there.

— Must I go to medical school and be a doctor like you，Dad?— No，you__________，son．You’re free to make your own decision．