【单选题】

以下叙述中正确的是（ ）。
A．Private Sub Form_Mouse Down(Button As Integer，Shift As Integer，- 　　　　　X As Single，Y As Single) 　　If Button=2 Then PopupMenu Bs，2 　　End Sub

B．Private Sub Form_MouseDown(Button As Integer，Shift As Integer，- 　　　　　　　　X As Single，Y As Single) 　　　　PopupMenu Bs 　　End Sub
C．Private Sub FOrm_MouseDown(Button As Integer，Shift As Integer，- 　　　　　　　X As Single，Y As Single) 　　　　PopupMenu Bs，0 　　End Sub
D．Private Sub Form_MouseDown(Button As Integer，Shin As Integer，- 　　　　　　　X As Single，Y As Single) 　　　　If(Button=vbLeftButton)Or(Button=vbRightButton)Then PopupMenu Bs 　　End Sub