Dim m2 As String

Private Sub Command1Click()

Dim flag(1 To 26) As Boolean

Dim num As Integer,t As Integer

Randomize

num = 1

Text3.Text = " "

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

Text3.Text = m2

End Sub

Private Sub Command2Click()

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

Dim k As String， c As Integer

s = Text1.Text

m = "abcdefghijklmnopqrstuvwxyz"

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       ③       

    If k = Mid(m, c, 1) Then

    continue = False

    End If

    c = c + 1

    Loop

   ④     

Next i

Text2.Text = result

End Sub

程序①处的代码是{#blank#}1{#/blank#}

程序②处的代码是{#blank#}2{#/blank#}

程序③处的代码是{#blank#}3{#/blank#}

程序④处的代码是{#blank#}4{#/blank#}

提示：年份值符合下列两种情况之一的是闰年。

⒈年份是4的倍数，但不是100的倍数；

⒉年份是400的倍数。

程序代码如下，为实现上述功能，请在画线处填写合适的代码。

Dim bh(10 000)As String        ‘存储学生编号

Dim jf(10 000)As Integer       ‘存储学生获得的积分值

Dim n As Integer               ‘存储学生总人数

Function Search(x As Integer)As Integer

    Search=0

    i=1：j=n：flag=True

    Do While i<=j And flag=True

      m=Int((i+i)／2)

      If x=jf(m) Then

         flag=False

             ①  

      Elself    ②     Then

        i=m+1

      Else

        j=m-1

      EndIf

    Loop

End Function

Private Sub Form_Load()

    ‘从数据库中读取学生编号和积分，分别存储到bh数组和jf数组中，并按积分值从小到大排序，显示在列表框List1中

End Sub

Private Sub Command1_Click()

    Dim Top As Integer，Bottom As Integer，Topxb As Integer，Bottomxb

As Integer

    List2．Clear

    Top=Val(Text1．Text)

    Bottom=Val(Text2．Text)

    If Top>Bottom Then t=Top：Top=Bottom：Bottom=t

    If Top>jf(n)Or Bottom<jf（1）Then Exit Sub

    Do While Search(Top)=0

      Top=Top+1

    Loop

    Do While Search(Bottom)=0

      Bottom=Bottom-1

    Loop

    Topxb=Search(Top)

    Do While jf(Topxb)=jf(Topxb-1)And Topxb>l

      Topxb=Topxb-1

    Loop

    Bottomxb=Search(Bottom)

    Do While jf(Bottomxb)=jf(Bottomxb+1)And Bottomxb<n

      Bottomxb=Bottomxb+1

    Loop

    For i=    ③    

       List2.AddItem bh(i)&"    "&jf(i)

    Next i

End Sub

①{#blank#}1{#/blank#} ②{#blank#}2{#/blank#} ③{#blank#}3{#/blank#} 

i=1:j=7:x=“high”

Do While i <=j

  m=(i+j)\2

  If a(m)=x Then Exit Do

  If a(m) > x Then

    j=m-1

 Else

   i=m+1

 End If

Loop

执行完上述代码后，根据最终变量值判断下列表达式，其中成立的是（  ）

Key = Int(Rnd * 49) * 2 + 1

s = 0: i = 1: j = 10

Do While i <= j

m = (i + j) \ 2

If Key = a(m) Then Exit Do If Key < a(m) Then

j = m - 1: s = 2 * s

Else

i = m + 1: s = 2 * s + 1

End If Loop

数组a(1)到a(10)的值依次为“2,6,7,15,20,24,27,43,52,63”，执行该程序段后，s的值不可能为（  ）