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
Inability to perform physical activity with discomfo falls under- 
Select and explain. 
A. NYHAclassl, B. 2, C. 3, D. 4
D: 4
Answer: D: 4 
Explanation: Ref: KV Krishna Das - Clinical Medicine 4th Edition pg no:170 NYHA Functional Classification Class I Dyspnea occurring at heavy, but accustomed activity Class II Dyspnea occurring on moderate exeion Class III Dyspnea during mild exeion or during daily routine activities Class IV Dyspnea even at rest.