Could it be in the restaurant you had dinner with me yesterday you left behind your wallet?
—— Oh, it’s raining hard outside. Mum, do you think the milkman will come? —— Of course. He will come on time _____it rains.
Though the book is a little expensive, it is _____.
It is required that students _____mobile phones at school, so seldom _____them using one.
——Tom is never late for work. Why is he absent today? —— Something _____to him.
—— Could you tell me his telephone number? —— _____the phone book and find it out yourself.