The correct answer is: B. Use the SETVER command
The SETVER command is used to set the version number of DOS that an application sees. If an application is expecting a certain version of DOS, and you are running a newer version, you can use the SETVER command to tell the application that it is running the version of DOS that it expects.
To use the SETVER command, type the following at the DOS prompt:
SETVER application_name version_number
For example, to tell an application that it is running DOS 5.0, you would type the following:
SETVER application_name 5.0
The SETVER command can be used to run applications that were written for older versions of DOS on newer versions of DOS. It can also be used to run multiple versions of DOS on the same computer.
Option A, Use the DOS+ command, is incorrect because the DOS+ command is not used to run applications that were written for older versions of DOS on newer versions of DOS. The DOS+ command is used to add additional features to DOS.
Option C, Restore the old DOS version, is incorrect because it is not necessary to restore the old DOS version in order to run an application that was written for an older version of DOS. The SETVER command can be used to tell the application that it is running the version of DOS that it expects.
Option D, Contact the application’s vendor support line, is incorrect because the application’s vendor support line may not be able to help you run the application on a newer version of DOS. The SETVER command can be used to tell the application that it is running the version of DOS that it expects.
Option E, None of the above, is incorrect because the SETVER command is the correct answer.