This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
[{'content': 'Conversion of fibrinogen to fibrin is by \nSelect and explain. \nA. Prothrombin, B. Factor XIII, C. Thrombin, D. Kallikrein', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Thrombin conves soluble fibrinogen to fibrin monomer Prothrombin is the precursor or thrombin Factor XIII is fibrin stabilization factor Kallikrein activates factor XII Ref: Medical Physiology Indu Khurana 2015 edition page No:154', 'role': 'assistant'}]