C knows the answer by deducing D is not yelling out the answer. 8 G" z. o6 v8 ~9 z3 LThat means D is not sure the answer by seeing one white and one black.公仔箱論壇8 q1 `4 F9 b/ e$ ]9 ~* M
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.