Private Sub Command1 click( )

  Dim a(1 to 3) as integer,k as integer,t as integer,s as integer

  a(1)=15: a(2)=36: a(3)=7

  s=0

  For k=2 to 3

if a(k)>a(1) then

  t=a(1):a(1)=a(k):a(k)=t

  s=s+1

End if

  Next k

  text1.text=str(a(1))

  text2.text=str(s)

End sub

 Private Sub Command1_Click()

   Dim x As Integer

   Dim y As Integer

   x = 900

   y = Abc(x)

   Label1．Caption = Str(y)

 End Sub

运行程序，单击命令按钮Command1后弹出如图所示的出错信息提示，引起该错误的语句是（   ）

Private sub Command1_click()

Dim s1 As String, s2 As String, t As String, ch As String

Dim i As Integer

s1 = Text1.Text

i = Len(s1)

t = "": s2 = ""

Do While i > 0

    ch = Mid(s1, i, 1)

    If ch >= "0" And ch <= "9" Then

        t = ch + t

    Else

    s2 = s2 + t +，   ①

    t = ""

End If

i = i + 1    ②

Loop

s2 = s2 + t

Text2.Text = s2

End sub

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

For i=1 To 3

k=“”

Fori-1 To 2*i-1

k=k+“*”

Next j

List1.AddItem k

Next i

该程序运行后，在列表框List1中显示的是（  ）