Which four types of variables must have their names preceded by a colon when they are referenced in trigger code?

Which four types of variables must have their names preceded by a colon when they are
referenced in trigger code?

A.
PL/SQL variables

B.
Form items

C.
global variables

D.
system variables

E.
parameters

Explanation:
D: Example:
On calling the
raiseEvent method, a trigger named WHEN-CUSTOM-JAVASCRIPT-EVENT is fired
on the server side.
declare
event_val varchar2(300):= :system.javascript_event_value;
begin
if (:system.javascript_event_name=’show’) then
handleShowEvent(event_val);
elsif(:system.javascript_event_name=’grab’) then
handleGrabEvent(event_val);
else
null;
end if;
end;