s=Text1.Text

 s1=" "

 For i=1 To Len(s)

    c=Mid(s, i, 1)

If  c>="A" And c<="Z"   Then

c=Chr(Asc(c)+32)                 '大写字母转化为小写字母

End if

s1=s1+c

Next i

 Text2.Text=s1

在文本框Textl中输入"ABcd12XY "，执行上述程序段后，文本框Textl显示的内容是(   )

Dim c As String, i As Integer

Dim s As String, s1 As String

s = "Jishu_Xuankao_2020"

s1 =""

For i = 1 To Len(s) Step 2

  c = Mid(s, i, l)

  If c >= "a" And c <= "z" Then s1=c+s1

Next i

Text1. Text = s1

执行该程序段后，文本框Text1显示的内容是（  ）

Private Sub Command1_Click()

  Dim a As Integer, b As Integer

  a = 10                                        '①

  b = 20                                        '②

  Text1.Text = "a+b=" + Val(a + b)              '③

End Sub                                         '④

Private Sub Command1_Click()

Dim u As Single, x As Single, y As Single, z As Single

u=Val(Text1.Text)

x=(u+10)/(u*u+8)

y=(u-1)/(x+u)

z=Sqr(x-y)

Text2.Text=Str(z)

End Sub

程序运行时，在文本框Text1中输入-1，单击命令按钮Command1，弹出如图所示的错误提示信息。产生此错误的语句是（  ）

五行程序代码中有{#blank#}1{#/blank#}处错误，在对应的横线上修改