A Japanese kindergarten entrance exam

There are four children in a room, two with black hats and two with white hats, but you don't know what colors to wear, A and B, C, there is a wall between D, so no one can see it. At the same time, no one can take off his hat or look back. After a moment of silence, some of the four children guessed the color of their hats. Who guessed A, B, C, and D? Why?

 

Analysis: The answer should be C.

 

First, a and B. If they don't see each other, they can be ruled out. If they're finished, analyze C, D.

First, stand in C's position:

If you are white, then D will know the answer, and D will definitely say you are black,

If you are black, you cannot determine the color of D.

Because c found that D could not find his own color, he must be black.