有如下 VB 程序段：

Const n = 7

Dim a(1 To 7) As Integer

Dim flag(1 To 7) As Integer       'flag 数组初始值均为 0 Dim k As Integer, t As Integer

a(1) = 18: a(2) = 34: a(3) = 56: a(4) = 23: a(5) = 29: a(6) = 39: a(7) = 72 k = (1 + 7) / 2

For i = 1 To n

    For j = 1 To n

        If a(j) > a(k) And flag(j) = 0 Then t = a(j): a(j) = a(k): a(k) = t

    Next j

    flag(k) = 1

    k = (k + 5) Mod 7 + 1

Next i

执行该段程序后，数组元素a(1)到a(7)的值为（    ）

A、29,23,18,72,56,39,34

B、39,56,72,18,23,29,34

C、34,39,56,72,18,23,29

D、34,29,23,18,72,56,39