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: Physiology
[{'content': 'Which of the following coagulation factor causes cross linking and stabilization of clot? \nSelect and explain. \nA. Factor XIII, B. Thrombin, C. Factor VIII, D. Factor IX', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Thrombin activates factor XIII (fibrin stabilizing factor) to factor XIIIa, which forms cross links and thereby stabilizes the clot.', 'role': 'assistant'}]