C knows the answer by deducing D is not yelling out the answer.5.39.217.76# z4 ]0 d, @) N; R
That means D is not sure the answer by seeing one white and one black.3 z( w$ m3 R: f9 N! W/ S. W6 i2 L! K4 @
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.