The preorder traversal sequence of a binary search tree is 30, 20, 10, 15, 25, 23,
39, 35, 42. Which one of the following is the postorder traversal sequence of the
same tree?
(A) 10,20,15,23,25,35, 42,39,30 (B) 15,10,25,23,20, 42,35,39,30
(C) 15,20,10,23,25, 42,35,39,30 (D) 15,10,23,25,20,35, 42,39,30