(a) One day, Meng's teacher scolded him because his hair was long. He felt sorry for his teacher. [grammatically OK, but it seems peculiar that he would feel sorry for his teacher after being scolded]
(b) After that, he went to a barber for a haircut.
(c) The next day, Peter [Do you mean Peter or Meng? Is this supposed to be a continuation of the same story?] was happy be