In case of fire, stay low to the ground in a smoky room, ________ smoke always rises towards the ceiling.
--- Hello! Is Mr. John in the office? --- Yes. But I’m sorry. He is busy _________ and can’t speak to you.
As a young man, there was __________ time __________ I hated to go to school .
—I am leaving for the States tomorrow, Caroline! —______
As we all know, many Chinese words have come into English, _____ typhoon, tofu and kung fu.
If better use is _______ of your spare time, you’ll make great progress in your study.