单项选择题

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 = 1 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Ctrl、Alt 键和鼠标左键
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