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: Pharmacology
After adding Drug A to an enzyme - substate reaction, Km remains same and Vmax decreases.
 Drug A is a 
Select and explain. 
A. Competitive antagonist, B. Non competitive antagonist, C. Agonist, D. None of the above
B: Non competitive antagonist
Answer: B: Non competitive antagonist 
Explanation: In Non competitive Antagonism: Km remains same, Vmax decreases.
In Competitive Antagonism: Km increases, Vmax remains same.