下面程序运行时，单击窗体后，窗体上显示的结果是( )。
Private Sub Form_Click
Dim I As Integer
Dim sum As Long
Dim t1 As Long
t1=1:sum=0
For 1=1 To 3
t1=t1*I
sum=sum+t1
Next I
Print sum
End Sub

A．3

B．9

C．5

D．6