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
Dicumarol is a drug that impairs the utilization of vitamin K by the liver. Dicumarol therapy would decrease the plasma concentration of which of the following procoagulants 
Select and explain. 
A. Prothrombin, B. Fibrinogen, C. Factor VIII, D. Factor V
A: Prothrombin
Answer: A: Prothrombin 
Explanation: Factor II is also called as Prothrombin, it is a vitamin K dependent clotting factor. Warfarin acts by inhibiting Vitamin K Epoxide Reductase Complex(VKORC) subunit 1 Ref: Ganong 25th ed/page 567