21.---Excuse me, Dad, but I am going to the club to meet my friends in the football team.

---OK.       

A. Good luck     B. Have fun    C. With pleasure    D. Congratulations

22. Scientists across the world agree that this is an invention of ____ great significance, ____ invention that will greatly change human life.

A. a; the     B. a; an     C. / ; the      D. / ; an