I was about to go to bed _____ someone knocked at the door.
— What happened then? — The Red Army _____ the bridge after they crossed it.
— Did you look up the time of planes to Beijing? — Yes, the earliest plane is to leave at 5:30 am.
His sister has recently got engaged ____ a foreign teacher, who has engaged ____ education research for years.
— Don’t be disappointed. Have another go, OK? — _______ .
— Why do you want the book so much? — ____, sir.