I don't know who invented ________ iphone,but I think it is ________ useful invention.
If you buy more than ten, they knock 20 pence off .
You’ll find this map of great ___________in helping you to get round London.
It is generally believed that teaching is ___________it is a science.
—John, there is_______Mr. Wilson on the phone for you.—I’m in bath.
The police are offering a __________to anyone who can give information about the lost key.