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
Registration of bih & death with a 6 monthly survey is done in - 
Select and explain. 
A. National sample survey, B. Vital statistical system, C. Census, D. Sample registration system
D: Sample registration system
Answer: D: Sample registration system 
Explanation: Ans. is 'd' i.e., Sample registration system