Answer is B, tested.

I think that is "A" correct.

If both the cron.allow and the cron.deny files do not exist, the default on current Ubuntu and other Debian-based systems is to allow all users to use the crontab command.

Anser A is correct

If the cron.allow file exists, a user must be listed in it to be allowed to use crontab. If the cron.allow file does not exist but the cron.deny file does exist, then a user must not be listed in the cron.deny file in order to use crontab. If neither of these files exist, then only the super user is allowed to use crontab.

A. Without additional configuration, all users may create user-specific crontabs. In Unix-based operating systems, the cron daemon is used to schedule and run commands periodically. The cron daemon reads the system crontab file /etc/crontab and user-specific crontab files located in the /var/spool/cron directory. By default, all users can create and modify their own user-specific crontab files without additional configuration. The cron.allow and cron.deny files are optional and can be used to control which users are allowed or denied permission to create or modify their own user-specific crontab files. Therefore, option A is correct. If neither cron.allow nor cron.deny exist in /etc/, all users can create their own user-specific crontab files without additional configuration. Options B, C, D, and E are incorrect because they do not describe the behavior of the cron daemon in the given scenario.

It is B: I checked the docu According to the Cron documentation, if neither cron.allow nor cron.deny exist in /etc/, the correct answer is B: "Without additional configuration, only root may create user specific crontabs.

Which one should I choose... the most voted or the one delivered by the system?

As access to cron without the existence of "cron.allow" or "cron.deny" files differs depending on which distro you're using, the only thing we know for sure is that root will be able to access it if neither file is present. "If neither of these files exist, the user’s access to cron job scheduling depends on the distribution used." source: LPIC-1 (102) (Version 5.0), page 206

Every distro has it own setttings

Answer B ...because: What is always true is that root may always create user crontabs in the way of run "crontab -e" with sudo (root privilegies) Others are wrong because: A. "all users may create user specific crontabs" is true only in certain distro - like Ubuntu. Indeed here is not permitted - Oracle Solaris? - https://docs.oracle.com/cd/E19253-01/817-0403/sysrescron-23/index.html E. deals with /etc/crond.conf that doesn't exist (in Ubuntu for sure) and doesn't appear in any crontab MAN C. and D. are frankly pure crap

just tested on centos 7

https://docs.oracle.com/cd/E19253-01/817-0403/sysrescron-23/index.html

"If neither cron.allow nor cron.deny exists, superuser privileges are required to run the crontab command." https://docs.oracle.com/cd/E19253-01/817-0403/sysrescron-23/index.html

The answer is B

Answer is B, tested on Rocky 8.4 When /etc/cron.deny is missing, other users cannot use crontab

This question is badly planned. I've already tested by deleting the two files (/etc/cron.allow and /etc/cron.deny). After that, I tested with different users and the OS allowed them to create crontabs. So, based on my test I could say the right answer is A. But also, I can see that other guys have tested and they have obtained different results. So, according to this last point, I think it depends on which distro you're using. Each time I feel more uncomfortable with this certification exams which bring to us badly planned questions, and this open the possibilities to fail the exam.