You plan to give an on-site presentation. The external display available for your audience is a 42-inch flat panel monitor.  You need to ensure that the presentation on the monitor of your computer is duplicated on the external monitor for the audience.  What should you do？（）

• A、Click the Show my desktop on the external display only option.
• B、Configure the Presentation settings to mirror your desktop on the external display. 
• C、Configure the Presentation settings to extend your desktop to the external display.
• D、Reduce the screen resolution of your primary display to a value equal to the maximum resolution of the external display.