2 若有以下程序代码 class Father{public void show(){}} class Son extends Father{ public void show(){} public void print(){} } class Main{ public static void main(String []s){ Father f; // 1 f=new Father(); //2 f.show(); // 3 f = new Son(); //4 f.show(); //5 f.print(); //6 } 则能实现多态的语句组合是( )