在C#中,下列代码的运行结果是()。 ( 选择一项 ) public class Student{ public virtual void Exam(){ Console.WriteLine(“学生都要考试”); } } public class Undergraduate:Student{ public new void Exam(){ base.Exam(); Console.WriteLiner(“大学生有选择考试科目的权利 "); } } public class Test{ static void Main(){ Student stu=new UndergraduateO; stu.Exam(); } }