This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Biostatistics, Subject name: Social & Preventive Medicine
Propoion of area from middle of curve to +1 standard detion- 
Select and explain. 
A. 0.68, B. 0.17, C. 0.12, D. 0.34
D: 0.34
Answer: D: 0.34 
Explanation: Ref:Parks 23rd edition pg 849. 1SD : confidence limit = 68% 2SD : confidence limit = 95% 3SD : confidence limit = 99.7% +/- 1SD: includes 68% of values, so +1SD will include half of it = 34%