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
Conversion of fibrinogen to fibrin is by 
Select and explain. 
A. Prothrombin, B. Factor XIII, C. Thrombin, D. Kallikrein
C: Thrombin
Answer: C: Thrombin 
Explanation: 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