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