Which statement replacing the comment will result in printing: B 2 ton ro B 2?

String s1 = "2 B or not 2 B";

String s2 = "";

for (int i = 0; i < s1.length(); i++) {

char ch = s1.charAt(i);

// replace with statement

}

System.out.println(s2);

s1 = ch + s1;

s1 = s1 + ch;

s2 = ch + s2;

s2 = s2 + ch;