B, pedigree can determine whether K is X recessive genetic disease, because S is X recessive genetic disease, father is normal, daughter K is normal, it can be X dominant and B is correct;

C and S fruits are accompanied by X dominant genetic disease or autosomal dominant genetic disease, 4 may be homozygote or dead heterozygote, and C is wrong;

D and S fruit genes are recessive and located on autosomes. K of the three pathogenic genes comes from the father, and D is wrong.

Therefore, choose: B.