複選題
(2) Which statement(s) is correct for an AVL tree?
(A) The absolute value of the level difference of any two leaves is at most one.
(B) The absolute value of the height difference of any two subtrees on the same level is at most one.
(C) A deletion needs at most two rotation operations to preserve an AVL tree to be a height-balanced tree.
(D) After a new node is inserted, the tree height will not increase if rotation operations are performed.