单选题：For an in-order threaded binary tree, if the pre-order and in-or

For an in-order threaded binary tree, if the pre-order and in-order traversal sequences are `B E A C F D` and `A E C B D F` respectively, which pair of nodes' left links are both threads? @[D](3)

A. B and E
B. E and F
C. C and F
D. C and D




A.B and E
B.E and F
C.C and F
D.C and D


答案：D