---Why do you keep the windows open on such a cold day? ---There are so many students here, so we want to keep the air nice and __.
His sister wanted to have him _____ the radio, but he had had it _____ already.
Simon likes playing ______ chess, while her brother is interested in playing _____ guitar.
—I’m very worried about tomorrow’s math test. I’m afraid I can’t pass this time. —______! I’m sure you’ll make it.
-- _____is that man over there? --- He is a doctor.
The patients will have to wait all day ______ the doctor works faster.