What command can be used to search the manual database for keywords?

The command to search the manual database for keywords is the one that starts with "man" followed by the option "-k". This command, when executed, allows users to search through the manual pages for specified keywords or strings. It essentially provides a way to find relevant commands or topics within the extensive documentation available in the system manuals, which can be particularly helpful when a user is unsure of the exact command they need but knows a related term.

Using this command, users can efficiently locate manuals that pertain to the keywords provided, facilitating quicker access to the necessary information without scrolling through all the manual pages manually. It enhances user experience by making the process of retrieving documentation more streamlined and manageable.

The other options do not represent valid commands for searching the manual database, which is why they serve different purposes or do not exist in the context of Linux commands.