C knows the answer by deducing D is not yelling out the answer.
9 r' V7 l4 u2 @# V0 m8 SThat means D is not sure the answer by seeing one white and one black.tvb now,tvbnow,bttvb% F8 v% o8 q' W1 n |" J1 E' X
C saw B is wearing the white, hence he is wearing the black |