Which code, inserted at line 4, guarantees that this program will output [1, 2]?

Given:

1. import java.util.*;
2. public class Example {
3. public static void main(String[] args) {
4. // insert code here
5. set.add(new Integer(2));
6. set.add(new Integer(1));
7. System.out.println(set);
8. }
9. }

Which code, inserted at line 4, guarantees that this program will output [1, 2]?

A.
Set set = new TreeSet();

B.
Set set = new HashSet();

C.
Set set = new SortedSet();

D.
List set = new SortedList();

E.
Set set = new LinkedHashSet();

Explanation: