Four hats and a wall

[The Rebel]

ok, here's one I was given at work today.

 

Four hostages are buried up to their necks in the ground, in a roughly straight line. One of them is seperated by a wall to the other three. As below

 

A || B C D

 

They are all facing the wall.

 

The terrorists have four hats, 2 black, 2 white, which are placed on the hostages. A and C have white hats on, B and D are wearing black hats. They are not allowed to talk, and they can not move their heads. The wall has no reflective surfaces or holes.

 

They are told that they will die unless one of them correctly shouts the colour hat they are wearing within 10minutes.

 

After 1 minute one of them calls out.

 

Which hostage is it?, and why are they correct?

[jordan]

Don't read ahead if you don't want the answer (or at least my guess at it):

 

 

 

C because he knows if his hat was the same as B then D would know right away. So his must be the other color.

 

 

What are the spoiler tags again, I can't remember and the BB thread wont open for me.

[Cap'n Refsmmat]

The tags are [/hide]

 

This (the puzzle) was asked before I believe.

[Sayonara]

Yes it was.