关于如下代码，下列选项正确的是（ ）class Test { public static void main(String[ ] args) { m(new GraduateStudent()); m(new Student()); m(new Person()); m(new Object()); } public static void m(Student x) { System.out.println(x.toString()); }}class GraduateStudent extends Student {}class Student extends Person { public String toString() { return "Student"; }}class Person extends Object { public String toString() { return "Person"; }}
选项：

A:m(new GraduateStudent()); 引起错误;
B:m(new Person()) ;引起错误;
C:m(new Object()); 引起错误;
D:m(new Student()) ;引起错误