程序运行时,能触发“Label2.Caption=″*″”代码执行的事件是（  ）

Dim a(1 To 10) As Integer

Dim s As String, n, i As Integer

s = "54851845236": n = Len(s)

For i = 1 To n - 1

a(i) = Val(Mid(s, i, 2))

Next i

For i = 1 To n - 2

k = i

For j = i + 1 To n - 1

If a(k) < a(j) Then k = j

Next

If k <> i Then

t = a(k): a(k) = a(i): a(i) = t

End If

Next i

Text1.Text = Str(a(1))

该程序段运行后，文本框 Text1 中显示的内容是：（  ）

For i=1 To 3

    For j=i+1 To 7

        If a(j)< a(i) Then

            k= a(j): a(j)= a(i): a(i)=k

            c=c+1

        End If

    Next j

    s= Str(a(i))+s

Next i

Text1.Text=Str(c) & ":" & s

数组元素a(1)至a(7)中值分别为3，9，1，5，8，6，2，该程序段运行后，文本框Text1中显示的内容是（   ）