**Core Concept**
The dependency ratio is a demographic measure used to assess the number of dependents (children and elderly) per 100 working-age individuals in a population. It is calculated by dividing the sum of the population aged 0-14 and 65+ years by the population aged 15-64 years.

**Why the Correct Answer is Right**
The numerator of the dependency ratio includes all age groups except those of working age. The working-age population is typically defined as individuals between 15 and 64 years old. The numerator includes children (0-14 years) and the elderly (65+ years), who are considered dependents because they are not economically active. The correct answer is the age group that is not included in the numerator.

**Why Each Wrong Option is Incorrect**
**Option A:** 15-64 years - This age group is actually included in the denominator of the dependency ratio, not the numerator.
**Option B:** 65+ years - This age group is included in the numerator as dependents.
**Option C:** 0-14 years - This age group is also included in the numerator as dependents.

**Clinical Pearl / High-Yield Fact**
Remember that the dependency ratio is a useful tool for policymakers to understand the economic burden of supporting dependents within a population.

**Correct Answer:** A. 15-64 years.