You have landed on an island of fun-loving logicians (hmmm ...) and don't know how to find your way home. After asking the first person you meet for directions, you are led to a secret, mystical place with a large stone engraved with the following drawing replete with directions:
"I want to go south," you explain. "Is this drawing correct?"
"Judge for yourself," answers the native. "I can only tell you that one of the arrows points south, but I cannot tell you which one. I cannot tell you how many arrows point in the right direction either, or you would know which way to go."
Show that you are bright enough to regain your bearings (whilst keeping your marbles) by working out which arrow points south.
[First fully explained answer carries the day.]
The "Pet Shop Boys" could help you too, if only you knew how.