请将实现以上功能的程序补充完整：

Private Sub Command1_Click( )

  x= Val (Text1.text)

  If  x>0   Then

    {#blank#}1{#/blank#} 

  ElseIf   {#blank#}2{#/blank#} Then

     y = 0

  ElseIf   x < 0   Then

     y = Abs(x)    

  End  If

  {#blank#}3{#/blank#}

End Sub

程序代码中,语句加框处有错，请改正。

Private Sub Command1_Click()

Dim s As String, sum As Integer

Dim i As Integer, j As Integer

List1.Clear

s = Text1.Text

n = len(s)

                               ’（1）

For i = 1 To n

  For j = 1 To n-i+1

     List1.AddItem        ’（2）

     sum = sum + 1

  Next j

Next i

List1.AddItem "总共有" + Str(sum)  + "个子串"

End Sub

⑴{#blank#}1{#/blank#} ⑵{#blank#}2{#/blank#} 

a(1) = 2

For i = 2 To 3

  a(i) = a(i - 1) - Int(Rnd() * 2)

  If i Mod 2 = 1 Then

    a(i) = a(i) + 1

  Else

    a(i) = a(i) - 1

  End If

Next i

执行程序后，a(2)和a(3)的值不可能的是（   ）

        PRIVATE SUB FORM_CLICK

        DIM A（4，4） AS INTEGER

        FOR I = 1 TO 4

           FOR J= 1 TO 4

              IF {#blank#}1{#/blank#}

                A（I，J）=1

              {#blank#}2{#/blank#}

               A（I，J）=0

              END IF

              PRINT A（I，j）;

              {#blank#}3{#/blank#}

            PRINT

              {#blank#}4{#/blank#}

        END SUB