The /etc/cron.allow and /etc/cron.deny files are used to control access to the crontab command and cron jobs for individual users. If neither of these files exists, then depending on site-dependent configuration parameters, only the superuser (root user) will be allowed to use this command, or all users will be able to use this command1. The default behavior of most Linux distributions is to allow all users to use the crontab command and have user specific crontabs if neither /etc/cron.allow nor /etc/cron.deny exists23. Therefore, option B is the correct answer. The other options are not true because:
Option A is false because it contradicts the default behavior of most Linux distributions.
Option C is false because the cron daemon will not refuse to start or report missing files in the system's logfile if neither /etc/cron.allow nor /etc/cron.deny exists. The cron daemon will start normally and use the default configuration parameters1.
Option D is false because the system administrator does not need to approve user specific crontabs explicitly. The user can create, edit, display, or remove their own crontab files without any intervention from the system administrator1. Reference:
How cron.allow and cron.deny can be used to limit access to crontab for a particular user | The Geek Search crontab(1) - cron - Debian bullseye - Debian Manpages Controlling Access to crontab (System Administration Guide: Basic Administration) - Oracle
/etc/cron.allow - Linux Bash Shell Scripting Tutorial Wiki - nixCraft