Review Question - QID 210666

A 12-year-old boy is brought to the emergency department with a hot, swollen, and painful knee. He was playing with his friends and accidentally bumped into one of them with his knee prior to presentation. His medical history is significant for an immunodeficiency syndrome, and he has been treated with long courses of antibiotics for multiple infections. His mother is concerned because he has also had significant bleeding that was hard to control following previous episodes of trauma. Laboratory tests are obtained with the following results:

Prothrombin time: Prolonged
Partial thromboplastin time: Prolonged
Bleeding time: Normal

The activity of which of the following circulating factors would most likely be affected by this patient's disorder?