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: Surgery
Half of the clot retraction is completed by? 
Select and explain. 
A. 24 hrs, B. Within 2 hrs, C. Within 15 minutes, D. Within 1 hour
D: Within 1 hour
Answer: D: Within 1 hour 
Explanation: None