(   )26. I saw your son ____ football on the playground when I called you yesterday.
       A. to play    B. played     C. playing
(   )27.I always have great fun ______ sports. 
       A. to do   B. do     C. doing
(   )28. --Would you mind ___ me English?
          –Of course not.
       A .to teach     B. teaching       C. teach     
(   )29.We will __ the school sports meeting next time.
       A. join        B. take part in      C. be