What is the file extension used by WIN95 to back up registry file when windows starts? A. .dat B. .dao C. .bak D. .tmp E. None of the above

The correct answer is C. .bak.

The Windows registry is a database that stores configuration settings for the Windows operating system and for installed applications. When Windows starts, it creates a backup of the registry file and stores it with the extension .bak. This backup file can be used to restore the registry if it becomes corrupted.

The other options are incorrect. The file extension .dat is used for data files, the file extension .dao is used for database files, the file extension .tmp is used for temporary files, and the option E is not a valid file extension.