设结点x和y是二叉树中任意的两个结点，在该二叉树的先根遍历序列中x在y之前，而在其后根遍历序列中x在y之后，则x和y的关系是(51)。

(88)

(89)

(71)data　effectively　is　crucial　for　success　in　today's　competitive　environment.　Managers　must　know　how　to　use　a　variety　of　tools.　Integrated　data　takes　information　from　different　sources　and　puts　it　together　in　a　meaningful　and　useful　way.　One　of　the　difficulties　of　this　is　the(72)in　hardware　and　software.(73)integration　uses　a　base　document　that　contains　copies　of　other　objects.(74)integration　uses　a　base　document　that　contains　the　current　or　most　recent　version　of　the　source　document　it　contains.(75)provides　an　overview　of　the　program　written　in"　plain"　English,　without　the　computer　syntax.

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(78)