Private Sub Command1Click()

Dim num(0 To 5) As Integer

Dim i As Integer, j As Integer

Dim t As Integer

num(0) = 4: num(1) = 7: num(2) = 2: num(3) = 0: num(4) = 3: num(5) = 9

i = 0: j = 1: t = 0

For i = 1 To 5 Step 1

  For j = i + 1 To 4 Step 1

  If num(i) > num(j) Then

  t = num(i)

  num(i) = num(j)

  num(j) = t

  End If

  Next j

Next i

For i = 1 To 5

List1.AddItem num(i)

Next i

End Sub

若采用选择排序算法对其进行从大到小排序，则第二趟的排序结果是（   ）

For i=1 to 3

    For j=1 to 5-i

        If a(j)>a(j+1) Then

            t=a(j)  :  a(j)=a(j+1)  :  a(j+1)=t

        End If

    Next j

    Text1.Text = Text1.Text + Str(a(i))

Next i

数组元素a(1)到a(5)的值依次为“3,9,6,8,4”。若该程序段执行后，文本框Text1显示的内容是（  ）

n = Val(Text1.Text)

For i = 1 to n

 a(i) = i

Next i

For i = 1 to n/2-1

 For j = n to 2*(i+1) step -2

  If      ①    Then t = a(j):a(j)=a(j-2):a(j-2)=t

 Next j

For j = 1 to n- i*2 step 2

  If      ②    Then t = a(j):a(j)=a(j+2):a(j+2)=t

 Next j

Next i

Private Sub Command2_Click()

Dim i As Integer, j As Integer, tmp As Integer

Dim s1 As String, t As Integer, s2 As String

t=1

For i=1 To n-2

    For j= To n Step 2     ‘改错

        If a(i)*t>a(j)*t Then

            tmp =a(i): a(i)= a(j): a(j)=tmp

        End if

    Next j

                   ‘填空①

Next i

For i =1 To n

    If     Then       ‘填空②

        s1 =s1 Str(a(i))

    Else

        s2=s2+Str(a(i))

    End If

Text2. Text=“奇数位：”+s1

Text3. Text=“偶数位：”+s2

End Sub

回答以下问题：

数据库文件“stud. accdb”信息如图所示。

程序界面如图所示，左边列表框List1中显示所有学生信息（包括编号和完成次数），单击“排序”按钮（Command），所有编号按照作业完成次数从高到低显示在列表框List2中。

代码如下：

Dim conn As New ADODB. Connection

Dim rs As New ADODB. Recordset

Dim n As Integer

Dim a(500)As String

Dim b(500)As Integer

Private Sub Fom Load()

    Dim i As Integer

    conn. Connection String="Provider=Mi-crosoft. AC

    A.OLEDB. 12.0；DATA Source="& App. Path &"\stud. accdb"

    conn Open

    Set rs. Active Connection=conn

    rs. Open "Select*From info"

    n=0

    Do While not rs.EOF            '到记录集最后一条记录后退出循环

        n=n+1

        a(n)=rs. fields("id")

        b(n)=rs. fields("finshed")

        rs. MoveNext                 '移动到下一条记录

    Loop

    For i=1 To n

        List1. AddItem a(i)+" "+Str(b(i))

    Next i

    rs. Close

    conn. Close

    Set rs= Nothing

    Set conn= Nothing

End sub

Private Sub Command1_Click()

    Dim i As Integer, j As Integer, t1 As Integer, t2 As String, k As Integer

    For i=1 To n-1             'n表示学生总数

        k=i           'k保存第i大的数，一开始假定是a(i)

        For j=i+1 To n

            If b(k)<b(j) Then k=j            '比较完成数

                ①      

            If    ②      Then

                t1=b(i): b(i)=b(k): b(k)=t1           '交换完成次数

                t2=a(i): a(i)=a(k): a(k)=t2           '交换编号

            End If

        Next j

    Next i

    For i=1 To n          '在列表框List2中输出排序结果

        Listt2. Addltem a(i)+" "+Str(b(i))

    Next i

End sub