複選題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).