Stay away from junk food, please. It’s bad for us，_________ for children! 

-- Is air the lightest thing in the world?-- Not            . Scientists from Zhejiang University have just developed the world’s lightest material.

— _______ does it take to get to your home town from here by coach?— Well, it takes a little over three hours to get there.

Though he has studied ____ at Russian for ten years,he can still _____speak the language.

----______do you ______of the sports shows ?   ----They’re interesting.