**Core Concept**
DALY stands for Disability-Adjusted Life Years, a measure used to quantify the burden of disease on a population. It takes into account the years of life lost due to premature death and the years lived with disability. The concept is crucial in global health and epidemiology for comparing the impact of various diseases and interventions.

**Why the Correct Answer is Right**
DALY is a composite measure that combines the years of life lost (YLL) and the years lived with disability (YLD). The formula for calculating DALY is YLL + YLD. YLL calculates the number of years of life lost due to premature death, while YLD estimates the number of years lived with disability. This measure helps in prioritizing health interventions and resource allocation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not accurately describe the components of the DALY measure.
**Option B:** This option is incorrect as it refers to a different concept, Quality-Adjusted Life Years (QALY), which is used in health economics to evaluate the cost-effectiveness of interventions.
**Option C:** This option is incorrect as it is a partial definition, but it does not mention the years lived with disability (YLD) component, which is essential for calculating DALY.

**Clinical Pearl / High-Yield Fact**
When interpreting DALY, it's essential to note that the weight given to YLL and YLD can vary depending on the disease and the population being studied. This allows for a more nuanced understanding of the disease burden and the impact of interventions.

**Correct Answer: C. Years of Life Lost (YLL) and Years Lived with Disability (YLD)**