The answer is C) B positive.
A mother has either AA or AO genotype. Since her daughter has OO genotype, the one O allele is from a father and one is from the mother. Thus, mother must have allele O. So mother's genotype is AO.
A mother with AO genotype will pass to her son either A or O allele. Since son is type B negative, it could inherit from mother only O allele. Son's genotype is BO. This means that he inherited from the father B allele.
Father has either BO or BB genotype. Since his daughter has OO genotype, she must inherit one O allele from the father. Thus, the father has BO genotype.
Talking of Rh, her son is type B negative. A negative Rh phenotype contains both recessive alleles r, so the mother must have allele r (she is either Rh+ heterozygous, or Rh- homozygous). The same is with father - he is either Rh+ heterozygous, or Rh- homozygous.
