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
The haemoglobin levels of pregnant females in a community was found to have a mean of 10.6 g/d1, and a standard detion of 2 g/dL. What is the minimum haemoglobin level below which 5% of the pregnant females will have their haemoglobin levels? 
Select and explain. 
A. 7.32, B. 8.64, C. 6.68, D. 8.96
C: 6.68
Answer: C: 6.68 
Explanation: Ans. c. 6.68