C knows the answer by deducing D is not yelling out the answer.公仔箱論壇2 q$ p& t5 O( V) I% P! d) I F
That means D is not sure the answer by seeing one white and one black. : z3 L5 J0 F1 l1 [3 \2 Q/ eC 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.