This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
The following agents may be used as prophylaxis In high attitude pulmonary edema - 
Select and explain. 
A. CAI, B. Aecnizolamide, C. Nifedipine, D. Digoxin
C: Nifedipine
Answer: C: Nifedipine 
Explanation: nifedipine is used in the prophylaxis of HAPE Drugs are not as effective as descent from altitude and oxygen in the treatment of high-altitude pulmonary edema (HAPE). Nifedipine, by reducing pulmonary aerial pressure, may be effective in treating HAPE. These agents must be staed 24 hours before ascent and continued for 48-72 hours at altitude Ref Davidson 23rd edition pg 460