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
All are to access platelet functions except -a) Prothrombin timeb) Bleeding timec) Clot retraction timed) Prothrombin deactivation 
Select and explain. 
A. ad, B. c, C. ac, D. ab
A: ad
Answer: A: ad 
Explanation: None