The answer is b. all of her sons will inherit the allele for hemophilia.
Hemophilia is X-linked recessive disorder. It is known that there are two X chromosomes (one from a mother and one from a father) in females and one X chromosome (from the mother) and one Y chromosomes (from the father) in males. In females, X-linked recessive disorder has the same pattern of inheritance as an autosomal recessive disorder.
So, if xh is recessive and xH is dominant allele, a mother which has xhxh genotype has the condition (so, c is not the right answer). Further, if a father has no condition, thus his genotype is xHy, their daughters will be carriers but without the condition (so, the choice a could be right only if we know that the father has hemophilia too (xhy). Therefore, since the mother (xhxh) will give her x chromosome to her sons, they will all inherit the allele for hemophilia, and choice b. is the right answer.
