Which configuration file should be modified to disable the ctrl-alt-delete key combination?

A.
/etc/keys

B.
/proc/keys

C.
/etc/inittab

D.
/proc/inittab

E.
/etc/reboot

Explanation/Reference:
In Linux, this keystroke combination is recognized by the keyboard device driver in the kernel. In the absence of more specific instructions, which will usually only be during system initialization, the kernel directly initiates a soft reboot in response. More commonly, the kernel will send a signal to the init  process, which will perform an administrator-configured task, such as running a script, or displaying an "end current session" box in KDE.
However, Linux systems can be configured to ignore the keystroke combination. The setting is usually in the inittab(5) configuration file under the keyword "ca".

In newer Linux systems (using upstart) /etc/inittab is replaced by /etc/event.d/