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
If the distribution of intra-ocular pressure (IOP) seen in 100 glaucoma patients has an average 30 mm with a SD of 1.0, what is the lower limit of the average IOP that can be expected 95% of times? 
Select and explain. 
A. 26, B. 28, C. 32, D. 259
B: 28
Answer: B: 28 
Explanation: In the given question, Mean (μ) = 30 mm and SD (σ) = 1.0 mm
Thus, 95% values are contained in the range of Mean ± 2 SD (µ ± 2σ) or 30 ± 2 (1)
So, 95% values are contained in the range 30 – 2 mm and 30 + 2 mm OR between 28 and 30 mm.