Dim a,b,c As Integer

   Dim s AS string

   a=9

   b=41

   c=2*(a+b)

   s=str(b+c)

For i = 1 To 10
 If d(i) >= 0 Then
   t=t+1
    List1.AddItem Str(d(i))
  Else
    t=t-1
    List2.AddItem Str(d(i))
Next
则该程序段出错的原因是缺少了（  ）

    Dim c(1 To 26) As Integer

    s = Text1.Text

    For i = 1 To Len(s)

        x = Mid(s, i, 1)

        If x >= "a" Then

            t = Asc(x) - Asc("a") + 1

        Else

            t = Asc(x) - Asc("A") + 1

        End If

        _______①_________

        If c(t) >= Max Then Max = c(t): _____②______

    Next i

    Text2.Text = Chr(f + Asc("A"))

划线处应该填入的正确语句是（  ）

Dim s As String, i As Integer, n As Integer

Dim ch As String, ans As Integer

s= Text1.Text

n Len(s): ans=0

For i=1 To n

    ch =Mid (s, i, 1)

    ans =ans *2+ Val(ch)

Next i

Text2 Text ans

若程序运行后Tex2中显示的是“38”，则Text中输入的是（  ）

图a

图b