**Core Concept**
The question tests knowledge of the role and responsibilities of a trained birth attendant (TBA) in maternal and child health, specifically in relation to population coverage.

**Why the Correct Answer is Right**
A trained birth attendant is a skilled healthcare provider who has received training in midwifery and basic obstetric care. They play a crucial role in reducing maternal and neonatal mortality by providing essential care during pregnancy, childbirth, and the postpartum period. TBAs are often the first point of contact for women in rural or underserved areas, where access to healthcare facilities may be limited.

**Why Each Wrong Option is Incorrect**

* **Option A:** This option is incorrect because TBAs typically serve a specific geographic area or community, rather than a random population.
* **Option B:** This option is incorrect because TBAs are not typically employed in large-scale healthcare facilities, but rather work in community settings.
* **Option C:** This option is incorrect because TBAs do not serve a population of a specific age range, but rather focus on providing care during the reproductive years.

**Clinical Pearl / High-Yield Fact**
TBAs are essential in reducing maternal and neonatal mortality, particularly in low-resource settings. They are often the primary providers of antenatal and postnatal care, and can significantly improve health outcomes for women and newborns.

**Correct Answer: D. The entire population in their catchment area.**