小明利用Visual Basic编写了“查找第二小的数”的程序,界面如图所示。程序随机产生50个范围在1~1000之间的随机整数,单击“查找”按钮,能够在标签Label1中显示第二小的数字。

(1)为了在列表框List1中加入随机产生的数字,小明在程序中写了语句“List1.AddItem Str(a(i))”,其中AddItem 是List1对象的__________(单选,填字母:
(2)实现上述功能的VB程序如下,请在划线处填入合适的代码。
Private Sub Command1_Click()
Dim n As Integer, i As Integer
Dim a(1 To 50) As Integer
Randomize
For i = 1 To 50
①___________
List1.AddItem Str(a(i))
Next i
If a(1) < a(2) Then
firstmin = a(1)
secondmin = a(2)
Else
firstmin = a(2)
secondmin = a(1)
End If
For i = 3 To 50
If a(i) < secondmin Then
②___________
secondmin = firstmin
firstmin = a(i)
Else
③____________
End If
End If
Next i
Label1.Caption = "第二小的数是" & Str(secondmin)
End Sub