单选题 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(ButtonAs Integer，Shift As Integer，X As Single，Y As Single) Print "Up" End Sub