The correct answer is rm -rf data_backup. The -r option stands for 'recursive' and is necessary to delete directories and their contents. The -f option stands for 'force', which prevents the command from prompting for confirmation. This combination is powerful and should be used with caution to avoid accidental data loss. rm data_backup is not correct because it will only work on individual files and will fail on directories. rmdir data_backup only removes empty directories, and rm -i data_backup will prompt for confirmation, which we want to avoid based on the question.