18. Which of the following statements are true?
(A) The search operation in a binary search tree of size n is O(logn).
(B) The height of a binary search tree of size n is Ω(logn).
(C) The search operation in an AVL tree of size n is O(logn).
(D) The height of an AVL tree of size n is O(logn).
(E) The delete operation in an AVL tree of size n is O(logn).