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.
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.