The Difference Between the Unordered_multimap Class and the Multimap Class

The difference between the unordered_multimap class and the multimap class is that

A) the unordered_multimap class uses the binary tree data structure for internal storage while the multimap class uses a hash table
B) the multimap class uses the binary tree data structure for internal storage while the unordered_multimap class uses a hash table
C) the keys in the unordered_multimap class are sorted while the keys in the multimap class are in no particular order
D) None of these