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
Mean ± 250 in normal distribution 
Select and explain. 
A. 68%, B. 95%, C. 99%, D. 50%
B: 95%
Answer: B: 95% 
Explanation: In normal distribution :

Mean ± 150 lovers 68% values.
Mean ± 250 lovers 95% values.
Mean ± 350 lovers 99% values.