I believe that instructors/teachers who sets the test, play on that system by switching the multichoice answers around and other tricks, because they don't want students to rely on crutches, so to speak, to remember the answer. When I remember anything that I read I often remember which side of the book it was on or sometimes I may remember where I was when I read it, even though it may be years ago. But, sometimes I also remember a fact about a subject, but can't remember which book I learnt it from or when or where I was living at the time. So the memory works in all kind of weird ways.
