C knows the answer by deducing D is not yelling out the answer.) d( y1 N9 Q6 R/ c+ D- \
That means D is not sure the answer by seeing one white and one black. : B. p7 o0 r! \* ~9 Htvb now,tvbnow,bttvbC 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.