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: Biochemistry
Vitamin K antagonizes 
Select and explain. 
A. Corticosteroids, B. Thrombin formation, C. Bishydroxy coumarin, D. Production of clotting factors by liver
C: Bishydroxy coumarin
Answer: C: Bishydroxy coumarin 
Explanation: Bishydroxy coumarin (dicoumarol), a vitamin K antagonist may be considered as an oral anticoagulant. 
This acts by reducing  the synthesis of certain clotting factors (ll, Vll, lX and X).

Ref : Lippincott’s illustrated reviews for biochemistry , 7th edition.