To answer this question, you need to understand the characteristics and purposes of different Java interfaces.
Option A) Set - This option is correct because a Set is a collection that stores unique elements. It does not allow duplicate elements and ensures that all elements are unique. Therefore, a Set interface would be the most suitable for storing unique object elements.
Option B) List - This option is incorrect because a List is a collection that allows duplicate elements and maintains the order of insertion. It does not guarantee uniqueness of elements, which is a requirement in this case.
Option C) Map - This option is incorrect because a Map is a collection that stores key-value pairs. It does not ensure uniqueness of elements, as duplicate values can exist for different keys.
Option D) Vector - This option is incorrect because a Vector is a resizable array that allows duplicate elements. It does not guarantee uniqueness of elements.
The correct answer is A) Set. This option is correct because a Set interface is designed specifically to store unique elements.