单选题

Which of the follwing sequence(s) could not be a postorder tree walk result of a binary search tree?

Question

下面序列哪个不可能是二叉搜索时的后序遍历结果？

A. 1,2,3,4,5

B. 3,5,1,4,2

C. 1,2,5,4,3

D. 5,4,3,2,1