What are the conditions for an optimal binary search tree and what is its advantage?

• A. The tree should not be modified and you should know how often the keys are accessed, it improves the lookup cost
• B. You should know the frequency of access of the keys, improves the lookup time
• C. The tree can be modified and you should know the number of elements in the tree before hand, it improves the deletion time
• D. None of the mentioned