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