Hi!
Usually computer programs have a lot of settings that, if not standardized, would make it super difficult to communicate with the operating system or other programs. Because of this, programs and the Windows Operating System use a special Registry system in order to standardize crucial settings for both applications and the operating system itself.
If you were to remove a directory to try to uninstall a program, you're leaving behind the files in the registry (don't worry though, it won't affect anything in terms of what your computer does) which can sometimes eat up space if there's enough of them.
Therefore, I would say your best bet is C. If the program adds information to the operating system.
I hope my answer helped!