下述代码执行后，有几个引用变量和几个对象？（）  
Student stu = new Student（“Mike”）； 
Student stua； 
Stua = stu；  

A. 2
B. 3
C. 4
D. 5

A. import java.sql.*； package school； class Student{ }
B. package school； import java.sql.*； class Student{ }
C. package school； class Student{ } import java.sql.*；
D. package school； import java.sql.*；private String name； class Student{ }

A. public static void main（String[] args）{}
B. public static void main（）{}
C. public static void main（String args[]）{}
D. public void static main（String[] args）{}