—Did you enjoy yourself at the party? —Yes, I’ve never been to _______ one before

 —Who is that boy?—Oh, he is Li Jing. He is ________ student in our class.

 —The little girl’s bedroom is very clean.—Yes. It’s much ________ than her ________.

Now the air in our city is _______ than it used to be．Something must be done to stop it．

The shop assistant showed her several mobile phones and she chose _______expensive one.