21. ---Why didn't you tell him about the meeting?

--- He rushed out of the room ______ I could say a word.

A. before           B. until             C. when            D. after

22. Research universities have to keep up with the latest computer and scientific hardware ________price.

A. far from         B. in need of        C. next to      D. regardless of

23. The children were _____ into different groups according to how much they know.

A. combined         B. classified              C. listed            D. clarified