1. (2017高三上·杭州模拟) 如图所示的VB程序中，输入以下程序代码，运行后单击命令按钮Command1，出现错误的提示图是：(   )

Private Sub Command1_Click()

Dim a(1 To 4) As Integer

Dim i As Integer

   a(1) = 1

 For i = 2 To 4

   a(i) = 2 * a(i - 1) + 1

 Next i

List1.AddItem Str(a(i))

End Sub

A . B . C . D .