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=2 Then      Print,"PC"    End If  End Sub  程序运行后,为了在窗体上输出“PC”,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