有如下VB程序段：

Dim a(1 To 10) As Integer

s = "7218634594": n = Len(s)

t = 0

For i = 1 To n - 1

    a(i) = Val(Mid(s， i， 2))

Next i

For i = 1 To n - 2 Step 2

    k = i

    For j = i + 2 To n - 1 Step 2

        If a(j) < a(k) Then k = j

    Next j

    If k <> i Then

        temp = a(i): a(i) = a(k): a(k) = temp: t = t + 1

    End If

Next i

Text1.Text = Str(t)

该程序段运行后，文本框Text1中显示的内容是（   ）

A、1

B、2

C、3

D、4