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
Surveillance is: 
Select and explain. 
A. Scrutiny of factors, B. Treatment of contacts, C. Both, D. None of the abov
A: Scrutiny of factors
Answer: A: Scrutiny of factors 
Explanation: Scrutiny of factors