In my opinion, the correct options are A. to ridicule the woman and C. to emphasize the woman's contradictions. The anonymous woman is prattling all the time about how she holds nothing against colored people, while showing her own deeply rooted prejudices. She is ridiculed because she is completely unaware of her inherent racism; also, because she thinks she is doing an honor to both her host and especially to the Negro singer Walter Williams by being there, as a white woman.
