C knows the answer by deducing D is not yelling out the answer. 7 G4 F+ }$ p5 s3 M& t公仔箱論壇That means D is not sure the answer by seeing one white and one black./ q+ C( k% x% I" j, Z
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.