Trees can stop the sand _____ towards the rich farmland in the south.
I don’t know____. Can you tell me?
--____ is your school from here? -- About one kilometer.
--____ does it take you to get to school? -- About twenty minutes.
--_____do you get to school? -- Of course by bus.
---- You like to surf the Internet. Do you know the meaning of “WWW”? ---- Of course. It means _______.