有以下VB程序段：

Dim a As String, b As String, p As String, s As String

a = Text1.Text

b = Text2.Text

c = Text3.Text

p = “ ”

For i = 1 To Len(a)

    If b = Mid(a, i, Len(b)) Then

        s = s + c

        p = p + Str(i)

    Else

        s = s + Mid(a, i, 1)

    End If

Next i

Label1.Caption = p

若文本框Text1中输入“Hello，Python！I use Python！”，文本框Text2中输入“Python”， 文本框Text3中输入“VB”运行该段程序后，标签Label1中显示的是(  )

A、7 20

B、8 21

C、12 26

D、13 27