VB程序运行界面如图2所示，在文本框Text1中输入查询的等级，单击“查询”按钮Command1，在列表框List1中显示所有该等级的学生学号和姓名，并按照学号从小到大排序，并在标签Label2处显示学生的人数，如果人数为0,则在列表框中显示“没有该等级的学生”。按此要求编写程序如下，在下划线处填上合适的代码。

Private Sub Command1_Click()

Dim stuna(1 To 100) As String '存放学生姓名的数组定义为stuna

Dim stunum(1 To 100) As String '存放学生学号的数组定义为stunum

Dim i As Integer, j As Integer, n As Integer

Dim t As String

Dim cn As New ADODB.Connection       '连接数据库

Dim rs As New ADODB.Recordset

Dim strSQL As String

cn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + App.Path + "\stugrade.accdb "

cn.Open

strSQL = "select * from      ①       where 语文等级='" + Text1.Text + "'"

Set rs.ActiveConnection = cn

rs.Open strSQL

n = 0

Do While Not rs.EOF

          ②    

   stuna(n) = rs.Fields("姓名").Value

   stunum(n) = rs.Fields("学号").Value

   rs.MoveNext       

Loop

rs.Close

cn.Close

Set rs = Nothing

Set cn = Nothing

List1.Clear '清除列表框

If n = 0 Then

   List1.AddItem "没有该等级的学生"

Else

   For i = 1 To n - 1       '按姓名排序

      For j = n To    ③    Step -1

         If        ④          Then      

            t = stunum(j): stunum(j) = stunum(j - 1): stunum(j - 1) = t

            t = stuna(j): stuna(j) = stuna(j - 1): stuna(j - 1) = t

         End If

     Next j

   Next i

   For i = 1 To n

      List1.AddItem stunum(i) + "  " + stuna(i)

   Next i

   Label2.Caption = "该等级的学生共有" + Str(n) + "名"

End If

End Sub

其中①处填入          ；②处填入           ；③处填入           ；④处填入           

a(l) = 5: a(2) = 16: a(3) = 22: a(4) = 28: a(5) = 35

a(6) = 43: a(7) = 52: a(8) = 67: a(9) = 78: a(10) = 89

i = 1: j = 10: n = 0: flag = True

Key = Val(Textl. Text)

Do While i <= j And flag = True

  m = (i + j) \ 2

  If a(m) = Key Then

    flag = False

  Elself a(m) < Key Then

    i = m + 1

    n = n - 1

  Else

    j = m - 1

    n = n + 1

  End If

Loop

变量n的值最终为0，则文本框Text1输入的数值范围可能是（  ）

i=1:j=7:x=45

Do While i <= j

    m = (i + j) \ 2

    If a(m) = x Then Exit Do    ‘Exit Do 退出 Do 循环

    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（  ）

n=0:i=l:j=6

key=Val(Text1.Text)

Do While i <=j

 m=(i+j) \ 2

 n=n+1

 If key=d(m) Then Exit Do

 If key > d(m) Then j=m-1 Else i=m+1

Loop

If i<=j Then s=Str(m-n) Else s=Str(n)

d(1)到 d(6)的值依次为“88，77， 53，47， 39，28”，输入某个key值后，运行该程序段后，变量s结果为1，则输入key的值是（  ）

Dim d(1 To 9) As Integer, s As String

Dim L As Integer, R As Integer, M As Integer, key As Integer

L = 1: R = 9

s = "": key =13

Do While L <= R

M = (L + R + 1) \ 2

If d(M) = key Then L = 10

If d(M) < key Then L = M + 1 Else R = M - 1

s = s + Str(M)

Loop