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: Social & Preventive Medicine
Not true about propagated epidemics ? 
Select and explain. 
A. Gradual rise, B. Gradual fall, C. Person to person transmission, D. No secondary wave
D: No secondary wave
Answer: D: No secondary wave 
Explanation: Ans. is 'd' i.e., No secondary wave