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
True regarding pertusis is all, except - 
Select and explain. 
A. Infectivity is highest in paroxysmal state, B. Cross immunity is not seen with B. parapertusis, C. Chronic carrier state is not seen, D. Secondary attack rate is 90%
A: Infectivity is highest in paroxysmal state
Answer: A: Infectivity is highest in paroxysmal state 
Explanation: None