C knows the answer by deducing D is not yelling out the answer.
" h& M! D/ t% ?8 A2 W' u3 FThat means D is not sure the answer by seeing one white and one black.
8 k, \+ @* l# g3 y3 Stvb now,tvbnow,bttvbC saw B is wearing the white, hence he is wearing the black |