C knows the answer by deducing D is not yelling out the answer.& f6 I8 q% E/ c* l# u V
That means D is not sure the answer by seeing one white and one black. , `8 \1 Z1 T& a5 z, |公仔箱論壇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.