This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Patient with hemophilia A have bleeding disorder because of 
Select and explain. 
A. Lack of platelet count, B. Lack of platelet adhesion, C. Lack of factor VIII a during activation of factor X in coagulation coscade, D. Release of thromboxane A2
C: Lack of factor VIII a during activation of factor X in coagulation coscade
Answer: C: Lack of factor VIII a during activation of factor X in coagulation coscade 
Explanation: Hemophilia A
X - linked disorder

90% cases - deficiency of factor 8
10% cases functional defect of factor 8

Factor VIII a complex is the most important activator of factor X required for conversion of prothrombin to thrombin.