You are designing a Window Phone 7 application that must be accepted by the Windows Phone Marketplace. The application must prompt users to confirm that they want to exit the application if they attempt to leave the main application page. If users do not want to exit the application, the application should return to the main page. You need to ensure that users can leave the application only after they confirm that they want to do so. What should you recommend?

A.
Override the OnManipulationCompleted event of the PhoneApplicationPage object. Provide a prompt to users to confirm they want to exit the application. If users do not want to exit, programmatically leave the event handler.

B.
Override the OnBackKeyPress event of the PhoneApplicationPage object. Provide a prompt to users to confirm they want to exit the application. If users do not want to exit, set the Cancel property of the event arguments for the event to true.

C.
Override the OnFragmentNavigation event of the PhoneApplicationPage object. Provide a prompt to users to confirm they want to exit the application. If users do not want to exit, programmatically leave the event handler.

D.
Override the OnFragmentNavigation event of the PhoneApplicationPage object. Provide a prompt to users to confirm they want to exit the application. If users do not want to exit, set the Cancel property of the event arguments for the event to true.