**Core Concept**
The Physical Quality of Life Index (PQLI) is a composite measure that assesses the quality of life in a country by combining three basic indicators: literacy rate, infant mortality rate, and life expectancy at age one. The PQLI provides a simplified and easy-to-understand indicator of a country's well-being.

**Why the Correct Answer is Right**
Income is not a component of the PQLI, which focuses on basic health and education indicators. The PQLI was developed to provide a more nuanced understanding of a country's quality of life beyond just its economic indicators. The inclusion of literacy rate, infant mortality rate, and life expectancy at age one allows for a more comprehensive assessment of a country's health and education systems. These indicators are essential for evaluating the overall well-being of a population, particularly in low- and middle-income countries.

**Why Each Wrong Option is Incorrect**
**Option B:** Literacy rate is indeed a component of the PQLI, making this option incorrect.
**Option C:** Life expectancy at age one is also a component of the PQLI, which means this option is incorrect as well.
**Option D:** Infant mortality rate is another component of the PQLI, making option D incorrect.

**Clinical Pearl / High-Yield Fact**
When evaluating a country's quality of life, it's essential to consider multiple indicators beyond just economic measures. The PQLI provides a useful framework for assessing a country's health and education systems, which can inform policy decisions and resource allocation.

**Correct Answer:** **✓ Correct Answer: A. Income**