**Core Concept**
The Physical Quality of Life Index (PQLI) is a composite measure that evaluates the overall well-being of a population by incorporating various indicators of health, education, and living standards. It is a multifaceted index that aims to provide a more comprehensive understanding of a country's quality of life beyond mere economic metrics.

**Why the Correct Answer is Right**
Per capita income is not a direct component of the Physical Quality of Life Index (PQLI). The PQLI focuses on health, education, and living standards, which are typically measured through indicators such as infant mortality, life expectancy at age one, and literacy rates. Per capita income, on the other hand, is an economic metric that does not directly reflect the quality of life. The PQLI was developed to address the limitations of using economic indicators alone to evaluate a country's well-being.

**Why Each Wrong Option is Incorrect**
**Option A:** Infant mortality is a key component of the PQLI, as it reflects the health status and quality of care received by infants.
**Option B:** Life expectancy at age one is also a component of the PQLI, as it provides insight into the mortality rates and health outcomes of a population.
**Option C:** Literacy rates are included in the PQLI to assess the education and cognitive abilities of a population.

**Clinical Pearl / High-Yield Fact**
The PQLI is a composite index that has been used to evaluate the quality of life in various countries, but it has its limitations, and more recent indices such as the Human Development Index (HDI) have been developed to provide a more comprehensive understanding of human well-being.

**✓ Correct Answer: D. Per capita income. Per capita income is not a direct component of the Physical Quality of Life Index (PQLI).**