阅读下列回答问题,在每小题提供的若干可选答案中,挑选一个正确答案。 【程序】 public class Point{ protected int x,y; public Point(int x,int y){ this.x=x; this.y=y; } public Point(int y){ this.x=0; this.y=y; } public Point(){ this.x=-1; this.y=-1; } public void show(){ System.out.println("("+x+","+y+")"); } } class NamedPoint extends Point{ private String name; NamedPoint(int x,int y,String name){ super(x,y); this.name=name; } NamedPoint(String name){ this.name=name; } public void show(){ System.out.println(name+"("+x+","+y+")"); } public static void main(String []args){ Point m=new Point(); m.show(); Point n=new Point(3); n.show(); NamedPoint p=new NamedPoint(4,5,"P"); p.show(); NamedPoint q=new NamedPoint("Q"); q.show(); } } 【问题】 (23) 程序运行产生的第 3 行输出为 。