This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Enzymes, Subject name: Biochemistry
A patient who wanted to go skiing in the Rockies took a medication to combat altitude sickness. A graph of this medication's mechanism of inhibition is shown. What type of inhibitor is this medication? 
Select and explain. 
A. Competitive, B. Non-competitive, C. Irreversible, D. Allosteric
B: Non-competitive
Answer: B: Non-competitive 
Explanation: In noncompetitive inhibition, the Km is not altered, whereas the Vmax is decreased. The drug used to treat altitude sickness is acetazolamide, which is a noncompetitive inhibitor of carbonic anhydrase. The graph is one of a pure noncompetitive inhibitor.