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: Medicine
A 50 year old man with aortic stenosis is doing exercise for 11 minutes according to brace protocol. Exercise stopped due to fatigue, Regional pressure gradient is 60 mm Hg between the two sides of the aortic valve. What is the best management 
Select and explain. 
A. Angiogram, B. Aortic valve replacement, C. Aortic ballooning to prevent further derangement, D. Observation
D: Observation
Answer: D: Observation 
Explanation: None