编写如下事件过程： Private Sub Form_ MouseDown (Button As Integer, _ Shift As Integer, X As Single, Y As Single)If Shift = 6 And Button = 2 Then Print "BBBB"End If End Sub程序运行后，为了在窗体上输出BBBB，应执行的操作为______ 。

A．同时按下Shift 键和鼠标左键

B．同时按下Ctrl、Alt 键和鼠标右键

C．同时按下Shift 键和鼠标右键

D．同时按下Ctrl、Alt 键和鼠标左键