下面叙述不正确的是（ ）。

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

A．数据的规范化
B．便于数据转换
C．避免数据丢失
D．防止不同模块之间数据的非法访问