What command is used to back up a MySQL database?

The command to back up a MySQL database using mysqldump is correctly represented in the first choice. The mysqldump utility is specifically designed for backing up MySQL databases by generating a text file with SQL statements that can recreate the database.

When using mysqldump, the -u option specifies the username that has access to the database, and the -p option prompts for the password for that user. Following that, you provide the name of the database you wish to back up. The output redirection operator (>) is used to write the output to a specified file, in this case, backup_file.sql, which will contain all necessary information to restore the database later.

Other options either utilize incorrect command names or lack the necessary syntax that mysqldump requires for successful execution. For example, mysqlbackup is not a command associated with standard MySQL server installations for backing up databases, and commands like backup-mysql do not exist in the MySQL suite. Only mysqldump is recognized for this specific purpose, making the first choice the valid and widely accepted option for backing up MySQL databases.