执行下列程序后，鼠标单击窗体，输出结果为
Private Sub Form_Click()
Print "Click"；
End Sub
Private Sub Form_MouseDown(Button As Integer，Shift As Integer，X As Single，Y As Single)
Print "Donw"
End Sub
Private Sub Form_MouseUp(Button As Integer，Shift As Integer，X As Single，Y As single)
Print "Up"
End Sub

A．DownUpClick

B．ClickDownUp

C．DownClickUp

D．UpDownclick