She _____ your birthday party, but she had to look after her mother in hospital．

A．should attend

B．ought to have attended

C．can have attended

D．must have attended

下列程序的功能是：将数据1，2，…，10写入顺序文件Base.txt中，请填空。
Private Sub Form_Click()
Dim i As Integer
Open______As#1
For i=1 To 10
Print #1，i
Next
Close #1
End Sub