Final answer:
Male offspring of a female carrier for hemophilia and an unaffected male have a 50% chance of having hemophilia, as the condition is X-linked recessive and males have only one X chromosome.
Step-by-step explanation:
The probability that a male offspring will have hemophilia when the mother is a carrier of the X-linked recessive disorder and the father is unaffected is 50 percent.
This is because females have two X chromosomes and are carriers if only one of the X chromosomes contains the recessive allele for hemophilia. Since males have one X and one Y chromosome, they will develop hemophilia if their single X chromosome carries the recessive allele. The mother will pass on either her normal X chromosome or her X chromosome with the recessive allele. If she passes on the affected X chromosome, the male child will have hemophilia because males have no second X chromosome to counter the recessive allele.
Answer choice 'a' from the options provided, indicating that females need two mutated X chromosomes to be hemophilic, explains why hemophilia is rarer in females. They would have to inherit two affected X chromosomes, one from each parent, which is statistically less likely than a male inheriting a single affected X chromosome from the mother.
Learn more about Hemophilia inheritance