To solve this question, the user needs to know what the TreeMap class is used for and which collection interface it implements.

The TreeMap class in Java is used to implement a map interface that sorts the keys in natural order. It provides an efficient means of storing key/value pairs in sorted order, making it useful for scenarios where you need to perform operations such as lookups, insertions, and deletions in a sorted collection.

Now, let's go through each option and explain why it is right or wrong:

A. SortedMap: This option is correct. TreeMap implements the SortedMap interface, which extends the Map interface and provides additional methods for retrieving and manipulating elements in a sorted order.

B. Tree: This option is incorrect. While TreeMap is implemented using a tree structure, it does not directly implement the Tree interface.

C. Set: This option is incorrect. TreeMap does not implement the Set interface, which is used for collections of unique elements.

D. SortedSet: This option is incorrect. TreeMap does not implement the SortedSet interface, which is used for sorted collections of unique elements.

The Answer is: A