Question (ix). What is a binary search tree? a) A tree where the value of the left node is less than (or equal to) the value of the middle node, which is, in turn, less than (or equal to) the value of the right node; b) A tree of degree D containing N nodes which has a height approximately logp N c) A binary tree in which all the leaves are on the same full level and the leaves of the last level can be searched as far to the left as possible; d) A binary tree where the value of each node is greater than the value of its left descendant and less than (or equal to) the value of its right descendant e) None of the above