Dim m2 As String

Private Sub Command1_Click()

Dim flag(1 To 26) As Boolean

Dim num As Integer,t As Integer

num = 1

For i = 1 To 26

    flag(i) = False

Next i

Do While num <= 26

    x = Int(Rnd * 26) + 97

         ①       

    If  flag(t) = False Then

        m2 = m2 + Chr(x)

        num = num + 1

           ②      

    End If

Loop

Text2.Text = m2

End Sub

Private Sub Command2_Click()

Dim s As String， m As String， result As String

Dim k As String， c As Integer

s = Text3.Text : m = Text1.Text

For i = 1 To Len(s)

    k = Mid(s, i, 1)

    If  k >= "A" And k <= "Z"  Then

        k = Chr(Asc(k) + 32)

    End If

    c = 1 : continue = True

    Do While continue=True

        If k = Mid(m, c, 1) Then

          continue = False

        End If

        c = c + 1

    Loop

      ③     

Next i

Text4.Text = result

End Sub

以上程序段运行时，为了实现上述功能，划线处应填入的代码为为：

① ； ② ；③。