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
Best test that shows the integrity of intrinsic pathway of clotting mechanism 
Select and explain. 
A. bleeding time, B. aPTT, C. prothrombin time, D. clotting time
B: aPTT
Answer: B: aPTT 
Explanation: Answer- B (aPTT)The aPTT measures the time necessary to generate fibrin from initiation of the intrinsic pathway.PTT measures the integrity of the intrinsic system (Factors XII, XI, VIII, IX) and common clotting pathways.