## Core Concept
The Physical Quality of Life Index (PQLI) is a measure used to assess the well-being of a country. It focuses on basic physical needs and takes into account several key indicators.

## Why the Correct Answer is Right
The PQLI is composed of three main components:
- Literacy rate
- Infant mortality rate
- Life expectancy at age one.
These components are chosen because they reflect fundamental aspects of a population's health and education.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is not specified, but typically, literacy rate is one of the components.
- **Option B:** Similarly, this option is unspecified, but infant mortality rate is another component.
- **Option C:** This option is also unspecified, but life expectancy at age one is a component.
- **Option D:** Since the correct answer is given as , we can infer that this option represents something not included in the PQLI.

## Why Each Wrong Option is Incorrect (continued)
Given that , and are components, any option not representing these would be incorrect in the context of being a component.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the PQLI does not directly account for income or economic factors, focusing instead on basic physical and educational outcomes.

## Correct Answer: D. Income.