Final answer:
HashSet has the advantage of allowing no duplicate values.
Step-by-step explanation:
The advantage that HashSet has over TreeSet is that it allows for no duplicate values. In a HashSet, each element is unique, meaning that if you try to add a duplicate value, it will not be added. This is useful when you want to store a collection of unique elements.
On the other hand, TreeSet does not allow duplicates either, but it provides the additional feature of ordering the elements. The elements in a TreeSet are stored in sorted order, according to their natural ordering or a custom comparator.
Therefore, the correct answer is c) No duplicate values.