下面代码的输出是什么？public class Base{    private String baseName = "base";    public Base()    {        callName();    }    public void callName()    {        System. out. println(baseName);    }    static class Sub extends Base    {        private String baseName = "sub";        public void callName()        {            System. out. println (baseName) ;        }    }    public static void main(String[] args)    {        Base b = new Sub();    }}

• A.null

• B.sub

• C.base