在窗体上画1个名为Text1的文本框和1个名为Label1的标签，再画4个名为Op1的单选按钮控件数组，其Ind

ex属性按季度顺序为0～3，如图1所示。在文件Sales.txt中按月份顺序存有某企业某年12个月的销售额。要求在程序执行时，鼠标单击一个单选按钮，则Text1中显示相应季度的销售总额，并把相应的文字显示在标签上。如图2所示是单击“第二季度”单选按钮所产生的结果。请选择可在空白处填写的合适语句()。 Option Base 1 Dim sales(12) As Long Private Sub Form_Load() Open "c:\sales.txt" For Input As #1 Fork= 1 To 12 Input #1, sales(k) Next k Close #1 End Sub Private Sub ______ (Index As Integer) Dim sum As Long, k As Integer, month As Integer sum=0 month=Index* Fork=1 To 3 month=month+1 sum=sum+sales(month) Next k Label1. Caption=______.Caption & "销售总额:" Text 1=sum End Sub

A．Op1_Click 3 Op1 (Index)

B．Op1_Click 0 Option1 (Index)

C．Option1_Cliek 1 Op1 (Index)

D．Option1_Click 2 Option1 (Index)