1.--Is John coming by train?    
   --He should, but he ____ not. He likes driving
      his car.           (2002高考题）
   A. must      B. can      C. need      D. may
2.It has been announced that candidates(候选人)
    ____ remain in their seats until all the papers
   have been collected. (2002上海高考题）
   A. can         B.will       C. may       D. shall
3.--I heard they went skiing in the mountains last
     winter.           (2002北京高考题）
  --It ____ true because there was little snow there.
   A. may not be               B. won’t be
   C. couldn’t be             D. mustn’t be