The preorder traversal of a binary search tree is 15, 10, 12, 11,20, 18, 16, 19. Which one of the following is the postorder traversal of the tree?
(A) 20, 19, 18, 16, 15, 12, 11,10
(B) 11, 12, 10, 16,19,18,20,15
(C) 19, 16, 18,20,11,12,10,15
(D) More than one of the above
(E) None of the above
