下面程序段的输出结果为( )。
public class Test int a, b;
Test()

a=100;
b=200;

Test(int x, int y)


a=x;
b=y;

public static void main(String args[])

Test Obj 1 = new Test(12,45 );
System.out.println("a="+Obj1.a+" b="+Obj1. b);
Test Obj2 = new Test();
System.out.println("a="+Obj2.a+" b="+Obj2. b);

A．a=100 b=200
a=12 b=45

B．a=12 b=45
a=100 b=200

C．a=12 b=200
a=100 b=45

D．a=100 b=45
a=12 b=200