在(1)~(3)处填上适当的语句,使程序能正常运行。. abstract class Person { public (1) show(); } class Student extends Person{ public (2) { System.out.println("Student");}} (3) { public void show(){ System.out.println("Teacher");}} public class Demo{ public static void main(String []args){ Person p; p=new Student(); p.show(); p=new Teacher(); p.show(); }}