Oscar

Four men are sentenced to death by firing squad: A, B, C and D.

The head executioner is in a good mood and decides to play a game with them and if they win he'll let them live.

They're buried neck deep so that only their heads are above the ground and can only look forward and nowhere else.

A, B and C are on buried on 1 side of a wall behind each other, facing the wall so that A can see the back of B and C's heads, B can see the back of C's head and C can only see the wall. The 4th man, D, is on the other side of the wall and cannot see the other 3.

Hats are put on the men; A gets a black hat, B gets a white hat, C gets a black hat and D gets a white hat.

They're told that there are 2 black hats and 2 white hats, but don't know that they were put on in an alternating sequence.

The head executioner then gives them five minutes for one person to say what the colour of their hat is.

It has to be the first sentence that comes out of any person's mouth; so the men can't communicate with each other.

At the last minute one man gets it right.

Who is he and how did he do it?