Who is most commonly affected by Hemophilia A?

Hemophilia A is a genetic disorder that primarily affects males due to its inheritance pattern. It is linked to the X chromosome, and since males have one X and one Y chromosome, the presence of the defective gene on their single X chromosome will manifest as the disease. In contrast, females have two X chromosomes, which means that if they inherit one affected X chromosome, the presence of a second normal X chromosome can prevent the disease from manifesting. Therefore, females can be carriers of the disorder but are far less likely to exhibit hemophilia A symptoms unless both of their X chromosomes carry the mutated gene, which is a rare occurrence.

This clear link to the X chromosome accounts for why the most commonly affected individuals are males, making the correct answer specific to them. While blood type may play roles in other medical conditions, it has no bearing on the susceptibility to hemophilia A, which is strictly a genetic issue.