55. What will be the output of the following code?

public class Test
{
public static void main( String []args ) {
StringBuffer a = new StringBuffer("A");
StringBuffer b = new StringBuffer("B");
operate( a,b );
System.out.println( a + "," + b );
}

public static void operate( StringBuffer x, StringBuffer y ) {
x.append( y );
y = x;
}
}

Select 1 correct answer:
A. A, B
B. The code will not compile.
C. B, A
D. AB, B