This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bleeding disorder, Subject name: Pathology
Patient with hemophilia A have bleeding disorder because of: 
Select and explain. 
A. Lack of platelet aggregation, B. Lack of reaction accelerator during activation of factor X in coagulation cascade, C. Neutralization of antithrombin III, D. Release of Thromboxane A2
B: Lack of reaction accelerator during activation of factor X in coagulation cascade
Answer: B: Lack of reaction accelerator during activation of factor X in coagulation cascade 
Explanation: Hemophilia A - X- linked disorder -90% cases- deficiency of factor 8 -10% cases - functional defect of factor 8 -Intrinsic Pathway affected -Factor VIIIa complex is the most impoant activator of factor X required for conversion of prothrombin to thrombin. -In symptomatic cases there is a tendency toward easy bruising and massive hemorrhage after trauma or operative procedures