We will have no water to drink _________ we don’t protect the earth.A. until B. if C. unless
—Do you spend a lot of time____ computer? —No, but I spend much time_____ doing my homework.
I’m sorry, I_________ the book in my home.
—What do cows eat? —They eat__________ grass.
Black broke his leg. He has just had_______ X-ray examination. _______ doctor said he needed _______ operation.
Mary likes ___________, but I ________listening to pop music.