Which change can you make to Target without affecting Client?

Given:

1. public class Target {
2. private int i = 0;
3. public int addOne() {
4. return ++i;
5. }
6. }

And:

1. public class Client {
2. public static void main(String[] args){
3. System.out.println(new Target().addOne());
4. }
5. }

Which change can you make to Target without affecting Client?

A.
Line 4 of class Target can be changed to return i++;

B.
Line 2 of class Target can be changed to private int i = 1;

C.
Line 3 of class Target can be changed to private int addOne(){

D.
Line 2 of class Target can be changed to private Integer i = 0;