There is_______ "s" and_______ "u" in the word "sun".
The math problem is _______ difficult and _______ of them can work it out.
_______ of the students in our class _______ interested in micro blogs (微博) on the Internet.
_______ great fun it is to play games on _______ QQ!
----Kathy, what do you think of my painting? ----_____________.
----I came to your office yesterday morning, but nobody was in. ----Oh, we__________ a meeting in the meeting room.