You Are Examining a 9-Year-Old Boy Who Is Brought in by His

You are examining a 9-year-old boy who is brought in by his parents for unexplained bleeding problems from birth. He experiences easy bruising, bleeding from the gums, and frequent epitaxis. His parents were first cousins, but they showed no bleeding problems. Hemostatic analysis of the boy's blood showed dramatically prolonged plasma prothrombin clotting time. Given the limited data in this case, a defect/deficiency in which of the following is most likely in this patient?

A) factor VIII
B) factor XI
C) factor XIII
D) fibrinogen
E) high-molecular-weight kininogen, HMWK