**Core Concept**
A Disability-Adjusted Life Year (DALY) is a measure of overall disease burden, expressed as the number of years lost due to ill-health, disability, or early death. It is a key metric in global health and epidemiology, used to quantify the impact of various health conditions on populations.

**Why the Correct Answer is Right**
DALYs are calculated by combining years of life lost (YLL) due to premature mortality, and years lived with disability (YLD). This metric takes into account the severity and prevalence of a disease, as well as its impact on quality of life. The World Health Organization (WHO) uses DALYs to track progress toward global health goals, such as reducing the burden of infectious diseases and non-communicable diseases.

**Why Each Wrong Option is Incorrect**
* **Option A:** Not applicable, as this option is missing.
* **Option B:** Incorrect, as this option is not a correct definition of a DALY.
* **Option C:** Incorrect, as this option is not a correct definition of a DALY.

**Clinical Pearl / High-Yield Fact**
When evaluating the burden of disease, it's essential to consider both mortality and morbidity rates. DALYs provide a comprehensive metric that accounts for the impact of various health conditions on populations, making it a valuable tool for global health decision-making.

**Correct Answer:**
. Life years lost due to ill-health, disability, or early death.