What will happend when you compile and run the following code:

public class X
{
    public static void concat(String s1, String s2) {s1 += s2;}

    public static void main(String argv[])
    {
        String s1 = "Hello ";
        String s2 = "World";
        concat(s1, s2);
        System.out.println(s1);
    }
}

A) Error: "Operator += illegal on immutable Strings"
B) Output Hello
C) Output Hello World
D) Output World
E) No output