Cruising Spots In Oregon

In un paese dell’America del sud, quattro uomini sono condannati a morte. Viene però data loro una possibilità per salvarsi la vita. Ognuno di loro porta un cappello : viene detto a loro che due indossano un cappello bianco, e due nero, ma nessuno di loro sa di quale colore è il proprio cappello. Per complicare le cose, vengono bloccati al suolo, one after another in single file so that it is impossible for them to turn around. Between A and B has built a wall beyond which you can not see. The Executioner tells them to be pardoned as long as 5 minutes in one of them guess the color of their hat. If, however, misses all four will be immediately executed. And 'forbidden to talk to each other and exchange all types of information.

After a minute one of the four convicted responds by saving the lives of everyone.

Can you say exactly which of the four answers and why it is so certain of its deduction?

There are pitfalls (there is, for example, a mirror on the wall or other strange things). There is no external element that can help them to answer and no way to communicate. Ultimately, A and B can not see anything but the front of the wall being in front of them, C can see B's hat, and D can see those B and C.