21. You are really very kind. I’ll never forget the      you have done to me.

A. favour      B. deed   C. help        D. good

22. ——Spacecraft “Discovery” has failed in the course of launch.

——_______? They have been preparing for the test.

A. How come  B. When  C. How  D. Why not

23. _______ different life today is ________ what it was 30 years ago.

A. How; from  B. What a; from

C. What; from  D. How; with