如果一个变量未经定义就直接使用，则该变量的类型为

A．log₂n
B．n²
C．On^1.5
D．n(n-1)/2

A．Private Sub Form_MouseDown(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_Mouse Down(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，Shift As Integer，_
X As Single，Y As Single)
If(Button=VbLeftBuaon)Or(Button=VbRighButton)Then PopupMenu Bs
End Sub