**Dependency Ratio**

**Core Concept**
The dependency ratio is a demographic measure that calculates the ratio of dependents (children and elderly) to the working-age population in a given population. It is an indicator of the potential burden on the working-age population to support the dependents.

**Why the Correct Answer is Right**
The correct answer is related to the calculation of the dependency ratio, which typically includes the proportion of the population that is either below the working age (children) or above the working age (elderly). The working-age population is usually defined as those between 15 and 64 years of age. The dependency ratio is calculated as follows: (0-14 years + 65 years and above) / 15-64 years. This ratio helps policymakers and planners to understand the potential strain on the working-age population to support the dependents.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the components of the dependency ratio.
**Option B:** This option is incorrect because it does not include the proportion of the population above the working age, which is also a dependency.
**Option C:** This option is incorrect because it is incomplete and does not accurately describe the components of the dependency ratio.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that the dependency ratio is a dynamic measure that changes over time due to demographic transitions, such as changes in fertility and mortality rates.

**Correct Answer: D. (0-14 years + 65 years and above) / 15-64 years.**