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
No chemoprophylaxis for - a)  Typhoidb)  Chicken poxc)  Influenzad)  Cholera 
Select and explain. 
A. b, B. ab, C. ab, D. bd
B: ab
Answer: B: ab 
Explanation: None