Which of the following registry hives stores information about the file extensions that are mapped to their corresponding applications?

HKEY_CURRENT_USER stores configuration settings and preferences scoped to the currently logged-in user profile, not system-wide file extension associations.

HKEY_USERS is a container hive that holds the root of all loaded user profile hives on the system, not file type or application mapping data.

HKEY_CLASSES_ROOT (HKCR) is a merged view of HKEY_LOCAL_MACHINE\Software\Classes and HKEY_CURRENT_USER\Software\Classes, and it is the canonical location where Windows stores file extension-to-application mappings (e.g., .docx to Word) as well as ProgIDs and COM object registrations used by the shell to open or act on files.

HKEY_LOCAL_MACHINE stores system-wide hardware configuration, installed software keys, and security settings, but file extension mappings are specifically organized and accessed through HKEY_CLASSES_ROOT.