Cindy,
How many posts is it going to take before you understand that the definition of 'special' is up to the person who wrote the test question?
Here's a suggestion for you. By now you should know the basic things that PLCs do. Go through the list of instructions supported by the PLC and pick the one that seems to you to be least connected to the basic functionality.
IM<HO, the basic instructions include anything related to Boolean logic, Timers, Counters, Math functions, and comparisons. Functionality beyond that such as PID, Shift registers, FIFO, LIFO, drum sequencers can be considered to be 'special' or 'advanced'.
Another approach you might take is to compare the functions offered on several different brands and models. Those functions offered on the fewest models of PLC could be considered 'special'.
I have a request to make of you. Once you get through this course, and have a little more time available, could you educate us Yanks on the logistics of these HNC courses. Are they offered in a traditional classroom setting where an instructor lectures on the topic of the day and the students struggle to take notes and try to understand? Is there a physical lab where you can practice? Is there ever a session where you have an opportunity to ask questions? What is the purpose of these courses?
For the most part, those of us who make our living practicing the craft of industrial automation, don't see the PLC portion as being of much use in the real world. Please help us to find out if our perception is accurate, or if it's biased by the types of questions we get asked.