21. -- Better get down to your work, Jack.

  --- _____________.

  A. It’s my pleasure                                   B. Not to mention it

  C. Mind your own business                     D. You’re welcome

22. After the quarrel, I tried all my best to fix the misunderstanding between us, but all my efforts seemed ______.

A. in trouble       B. in case      C. in time                   D. in vain