Private Sub Command1_Click()

    Dim s As String, s1 As String, c As String

    s = Text1.Text

    For i = 1 To Len(s)

        c = Mid(s, i, 1)

        s1 =    ⑴   

        For j =    ⑵   

            If c <> Mid(s, j, 1) Then

                s1 = s1 + Mid(s, j, 1)

            End If

        Next j

           ⑶    

    Next i

Text2.Text = s

End Sub

s = "ABCDEF"

For i = 1 To Len(s)

    a = Int(Rnd * 3 + 1)

    b = Mid(s, a Mod 6 + 1, 1)

    ch = ch + Chr(Asc(b) + 32)

Next i

执行该程序后，变量ch的值可能是（    ）

程序空白处应填写的语句是：{#blank#}1{#/blank#}。