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: Unknown
Thrombosthenin is: 
Select and explain. 
A. Coagulation factor, B. Contractile protein, C. A thrombosis promoting protein, D. A protein regulating platelet production
B: Contractile protein
Answer: B: Contractile protein 
Explanation: Thrombosthenin, platelet contractile proteins contract and help in clot retraction 48 hours after injury. the contractile protein of platelets is, responsible for clot retraction , platelet aggregation, and release of ADP and other biologic amines essential to platelet function.