单选题：Given the shape of a binary tree shown by the figure below. If

Given the shape of a binary tree shown by the figure below. If its postorder traversal sequence is { `e`, `a`, `c`, `b`, `d`, `f` }, then the node on the same level of `b` must be: @[A](3)




A. `a`
B. `e`
C. `c`
D. None




A.`a`
B.`e`
C.`c`
D.None


答案：A