It is impossible to reinstall an application only using windows control panel FYI

Seems like this question is referring to obj 3.1/3.2 A. You can uninstall using windows control panel but can't reinstall B. same as above C. Can replace missing or corrupt files while preserving host settings (correct IMO) D. Silly. Repair Application Windows apps can become corrupt for a variety of reasons, including disk errors, poor coding, errant updates, or apps left open when Windows is shut down or restarted. To get a faulty application working again, repair the application. You can repair an application through Control Panel’s Programs and Features applet. To start the process, click the application, then click Uninstall/Change. If a repair option is available, select it to repair the app. If an app lacks a repair option, uninstall the app and reinstall it instead. - Mike Meyers' ebook

You’ll experience this sort of scenario with error messages such as “missing DLL” or “cannot open file xyz.” The easiest fix is to first try to "reinstall the program", and check for any special instructions about versions of support files. Barring that, the usual second step for either issue is to perform an Internet search for the missing DLL or file that fails to open, along with the name of the program you’re trying to use. -Mike Meyers ebook Maybe try B and reinstall the app first?

Is it talking about DLL files?

Why not D?