If no one tells him where the bell is, everyone will receive a failing grade for the whole year. The students know that everyone is equally guilty, and all know where the bell is. Let's turn up the juice a little more. This is similar to one of the dilemmas mentioned in the first chapter. You and ninety-nine friends are held captive in a problem box.
Every person is in a separate soundproof cubicle.
Each cubicle has a button. If you push the button you die. But if no one pushes the button before the big clock of doom on the wall strikes twelve, everyone dies. The worst possible outcome is for no one to push the button. Then you die.