--What kind of ________ makes 3G cellphones so popular with the young? --Video communication, I think.

When the headmaster spoke out his plan, the _______of the students in the class________  against it .

 —Excuse me, may I ask you some questions? ---Sorry, I’m too busy and haven’t even a minute to________.

I want to buy two ___ of colour ___.

At the meeting they discussed three dif-ferent_______to the study of mathematics。