C knows the answer by deducing D is not yelling out the answer.公仔箱論壇7 T2 u; R# ~: d) x
That means D is not sure the answer by seeing one white and one black. ' K @4 P1 s& u6 y g5.39.217.77:8898C 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.