________ in the queue for half an hour, the old man suddenly realized he had left the cheque in the car.
—Did you look up the time of trains to Shanghai? —Yes, the earliest train is_____to leave at 5:30 am.
She stepped into the bedroom quietly_____she might wake up her roommates.
Many people have been ill from a strange disease these days,_____ we’ve never heard of before.
—He_____ to the meeting. Have you informed him of it? —Sorry. I_____ to.
It is not enough only_____the rules of grammar if you want to learn English well.