## Core Concept
The Physical Quality of Life Index (PQLI) is an attempt to measure the quality of life or well-being of a country. It is a composite index that averages three basic literacy, infant mortality, and life expectancy at age one.

## Why the Correct Answer is Right
The PQLI combines three key indicators:
- Literacy rate
- Infant mortality rate
- Life expectancy at age one.
These indicators reflect basic needs and outcomes in health and education.

## Why Each Wrong Option is Incorrect
- **Option A:** Literacy rate is one of the indicators.
- **Option B:** Infant mortality rate is also an indicator.
- **Option C:** Life expectancy at age one is an indicator.
- **Option D:** GDP per capita is not an indicator of PQLI; it's a component of other indices like the Human Development Index (HDI).

## Clinical Pearl / High-Yield Fact
A key point to remember is that PQLI does not directly account for GDP or income levels, focusing instead on direct measures of health and education.

## Correct Answer Line
**Correct Answer: D. GDP per capita.**