22. The two boys fought and fought until one ______.
I happened __________ with him when he was hit by a stone.
You'd better not phone me between two and six o'clock this afternoon; I __________ a speech then.
By the middle of the 21st century, the vast majority of the world's population __________ in cities rather than in the country.
-I will call on you at 9:00 tomorrow morning.-Sorry, I __________ the flight to Sanya then.
My wife __________ the night shift when my plane __________. That's why no one is to meet me at the airport today.