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
Birth weight of all 10 babies born an in a nursing home on a day was 2.7 kg. Standard deviation is - 
Select and explain. 
A. 0, B. 1, C. 0. 27, D. 2.7
A: 0
Answer: A: 0 
Explanation: Standard deviation is a measure of dispersion from central value.
In the question, there is only one central value (2.7 Kg) as all 10 babies have same weight. Thus, there is no dispersion.