public void Shrink()
 {
     this.base_Person = new ShortPerson();
 }
 public void Enlarge()
 {
     this.base_Person = new TallPerson();;
 }
 public StudentPolymorphism3(string name)
 {
     this.base_Person = new PersonPolymorphism1();
     this.name        = name;
 }