21. ____ wide spread of H1N1 is _____ challenge for the whole world. Confidence, cooperation and responsibility are keys to overcoming it.

A. A; the        B. A; a            C. The; the             D. The; a

22. ---Which of the two shirts will you take, the white one or the pink one?

   --- ____. They match my black suit perfectly.

A. None           B. Neither              C. All                D. Both