---How can you believe ____________? He is dishonest.---Oh, I see.
In our class _____ of the students _____boys.
—_____ you _____ your homework yet?—Yes, I _____ it ten minutes ago.
It’s necessary for you _____ exercise every day.
—Could you tell me _____?—Sorry, I don’t know.
The supermarket provides customers _____ plastic bags for free.