C knows the answer by deducing D is not yelling out the answer. ! u8 P0 L* o, }" g `/ wThat means D is not sure the answer by seeing one white and one black.公仔箱論壇( o- b" p: X8 x' K4 Z% b/ J
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.