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 `D A B C F E` and `B A C D E F` respectively, which pair of nodes' left links are both threads? @[D](3)

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




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


答案：D