C knows the answer by deducing D is not yelling out the answer. 6 Q) @- @4 k9 o$ h- ^. N公仔箱論壇That means D is not sure the answer by seeing one white and one black. 7 b( W) l% N" ?' z, V. ~9 y2 [5 ^* H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.