C knows the answer by deducing D is not yelling out the answer.
6 d7 h' I% M1 s# |tvb now,tvbnow,bttvbThat means D is not sure the answer by seeing one white and one black.tvb now,tvbnow,bttvb# Y' a* O1 `: D) ?% j, J
C saw B is wearing the white, hence he is wearing the black |