To prevent a specific user from scheduling tasks with at, what should the administrator do?

A.
Add the specific user to /etc/at.allow file.

B.
Add the specific user to [deny] section in the /etc/atd.conf file.

C.
Add the specific user to /etc/at.deny file.

D.
Add the specific user to nojobs group.

E.
Run the following: atd -deny [user].

Explanation/Reference:
From the man pages:
The /etc/at.allow and /etc/at.deny files determine which user can submit commands for later execution via at(1) or batch(1).
If the file /etc/at.allow exists, only usernames mentioned in it are allowed to use at.
If /etc/at.allow does not exist, /etc/at.deny is checked.