Which of the calls modifies the string s? : Questions « Utility Classes « SCJP

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public class MainClass{
    public static void main(String[] argv){
       String s = "abc";
    }
}
    

A.      s.append("aaa");
B.      s.trim();
C.      s.substring(3);
D.      s.replace('z', 'a');
E.      s.concat(s);
F.      None of the above