单选题假定已经在菜单编辑器中建立了窗体的弹出式菜单，其顶级菜单项的名称为al，其“可见”属性为false，程序运行后，单击鼠标左键或右键都能弹出菜单的事件过程是______。

A、 Private Sub Form_MouseDown(Button As Integer, _Shift As Integer, X As Single,Y As Single)If Button=1 and Button=2 ThenPopupMenu alEnd IfEnd Sub
B、 Private Sub Form_MouseDown (Button As Integer, _Shift As Integer, X As Single,Y As Single)PopupMenu alEnd Sub
C、 Private Sub Form_MouseDown (Button As Integer, _Shift As Integer, X As Single，Y As Single)If Button=1 ThenPopupMenu alEnd IfEnd Sub
D、 Private Sub Form_MouseDown(Button As Integer, _Shift As Integer. X As Single,Y As Single)If Button=2 ThenPopupMenu alEnd IfEnd Sub

【正确答案】 B

【答案解析】[解析] 本题考查弹出菜单的应用与鼠标按键的判断。PopupMenu方法用来显示弹出菜单，将PopupMenu方法放在MouseDown事件中，默认可以响应所有的鼠标键的单击操作，语法格式为：Object.PopupMenu menuname，flags，x，y，boldcommand其中：Object(对象)——窗体名。Menuname(菜单名)——指在菜单编辑器中定义的主菜单项名。Button=1表示鼠标左键，Button=2表示鼠标右键。本题要求程序运行后，单击鼠标左键或右键都能弹出菜单的事件过程。