C knows the answer by deducing D is not yelling out the answer.公仔箱論壇$ A. ~8 B' K/ a6 ~5 O, A7 H
That means D is not sure the answer by seeing one white and one black. & j9 i- P* z( m5 _9 F$ i4 ?C saw B is wearing the white, hence he is wearing the black
C, because he saw B's hat is white and he knows D can see the color of B's and his hat. If B and his hat has the same color, D would speak out. But D kept silent, so C knows that his hat's color must be different.