Answer: A
Balancing of a BST is important to give the desired O(log n) search time. If the tree is unbalanced, search time could be as bad as O(n). While O(n) is not always bad, we expect a lookup table to have a time of O(1) or O(log n) because lookup is done frequently, often in a loop. (Unless the table is known to be small, in which O(n) is okay.)