1.He ___ have completed his work; otherwise, he wouldn't be enjoying himself by the seaside.
   A. should       B. must        C. wouldn't       D. can't  
2. I _____ have been more than six years old when the accident happened.
   A. shouldn't      B. couldn't     C. mustn't       D. needn't
3. This cake is very sweet. You ____ a lot of sugar in it.  
   A. should put      B. could have put      C. might put    D. must have put