单选题：To list the directory in a hierarchical file system with the for

To list the directory in a hierarchical file system with the format of files that are of depth `di` will have their names indented by `di` tabs,
which of the following traversals is the most suitable one. @[A](3)

A. pre-order
B. in-order
C. post-order
D. level-order




A.pre-order
B.in-order
C.post-order
D.level-order


答案：A