C knows the answer by deducing D is not yelling out the answer. / |' z% ^5 f7 [9 n/ j: h: q( y+ x5.39.217.77:8898That means D is not sure the answer by seeing one white and one black. - ?% ]! J: c t' M0 w9 @% bC 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.