**Core Concept**
A normal distribution of Fasting Blood Sugar (FBS) in a population indicates that the values follow a bell-shaped curve, with the majority of the population's values clustered around the mean. In a normal distribution, about 95% of the values lie within two standard deviations of the mean.

**Why the Correct Answer is Right**
To determine the range within which 95% of the population's FBS values lie, we use the 68-95-99.7 rule (also known as the empirical rule). This rule states that about 68% of the values lie within one standard deviation of the mean, about 95% lie within two standard deviations, and about 99.7% lie within three standard deviations. Given that the mean FBS is 105 mg% and the standard deviation is 10 mg%, we can calculate the range within which 95% of the population's FBS values lie by finding the 2.5th and 97.5th percentiles.

**Why Each Wrong Option is Incorrect**
**Option A:** This option does not provide a valid range for 95% of the population's FBS values.
**Option B:** This option is incorrect because it does not accurately reflect the range within which 95% of the population's FBS values lie.
**Option D:** This option is also incorrect because it does not accurately reflect the range within which 95% of the population's FBS values lie.

**Clinical Pearl / High-Yield Fact**
When dealing with normally distributed data, the 68-95-99.7 rule is a useful tool for quickly estimating the range within which a certain percentage of the values lie.

**Correct Answer:** 95% of the population will have FBS within 85-125 mg%.