图1
   图2

 程序代码如下：

Private Sub Command1_Click()

  Dim i As Integer

  List1.Clear            '清除列表框内容

End Sub

Private Function f(x As Integer) As Boolean  '自定义函数f,返回值为逻辑型

  Dim j As Integer

  f = True

  For j = 2 To Int(Sqr(x))

    If x Mod j = 0 Then

      f =     ③      '函数返回值

      Exit For           '跳出For循环

    End If

  Next j

End Function

实现上述功能的VB代码如下, 但划线处代码有错，请改正。

Dim a(1 To 50) As Integer

Private Sub Command1_Click()

Dim i As Integer

k = 0: i = 3

Do While i <= 100

   If  ① prime(i)   Then      ‘⑴

      k = k + 1

      a(k) = i

   End If  

   i = i + 2

Loop

For i = 2 To k

   If   ②a(i) = a(i +1)+2   Then   ‘⑵

      List1.AddItem Str(a(i - 1)) + "和" + Str(a(i))

   End If

Next i

End Sub

Function prime(x As Integer) As Boolean

prime = False

For i = 2 To Int(Sqr(x))

   If  x Mod i = 0  Then

      prime = True

      Exit For

   End If

Next i

End Function

① {#blank#}1{#/blank#}  ②{#blank#}2{#/blank#}  

For i = 100 To 999 lag = True: j = 2

Do While j < i And flag

Loop

If flag Then List1.AddItem Str(i) Next i

方框中的代码由以下四部分组成：①End If   ②If i Mod j = 0 Then   ③j = j + 1

④flag = False。代码顺序正确的是（  ）

程序部分代码如下：

Private Sub Command1_Click()

Dim n, m, s, i, j, count As Long

Dim flag As Boolean

Dim a(1 To 100) As Integer

n = Val(Text1.Text)

count = 0

  ①  

For i = 0 to s-1

 m = i

 For j = 1 To n

 a(j) = m Mod 2

 m = m \ 2

Next j

flag = True

For j = 1 To n - 1

 If  ②  Then flag = false: exit For

Next j

If flag = True Then  ③  

Next i

Label1.Caption =“可行方案共”+ Str(count) + “种”

End Sub