I added and antry in /etc/sudoers file. But I can still execute the command.
## Allows members of the users group to shutdown this system
# %users localhost=/sbin/shutdown -h now
champ elephant2=/bin/mount /dev/cdrom ALL ------------> this one
[champ@elephant2 ~]$ sudo /bin/mount /dev/cdrom
[sudo] password for champ:
Sorry, user champ is not allowed to execute '/bin/mount /dev/cdrom' as root on elephant2.