C knows the answer by deducing D is not yelling out the answer.' H2 ^" |' n* `. S* j" E/ W: v
That means D is not sure the answer by seeing one white and one black. 7 M3 _7 M/ K% [! mC 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.