i want to be a model student. what shall i do? 　 　
  i should be polite. i should study hard. i should capful and helpful. i should walk in the corridors. i should throw rubbish in the bin. i should be quiet in the library. i shouldn’t walk and run on the grass. i shouldn’t throw rubbish on the floor. i shouldn’t run in the corridors. i shouldn’t fight. i shouldn’t be noisy in the library. 　  
how about you?