**Core Concept**
The Physical Quality of Life Index (PQLI) is a composite index used to measure the quality of life in a country, focusing on basic needs such as health, education, and living standards.

**Why the Correct Answer is Right**
The PQLI was developed by Morris David Morris in 1979. It incorporates three key indicators: infant mortality rate (a measure of healthcare quality), life expectancy at one year of age (reflecting healthcare and living standards), and literacy rate (indicating education and human development). These indicators are used to create a comprehensive picture of a country's quality of life.

**Why Each Wrong Option is Incorrect**
**Option B:** Maternal mortality, Life expectancy and Literacy. While maternal mortality is an important health indicator, it is not part of the PQLI. The PQLI focuses on infant mortality instead.
**Option C:** Disability rate, Pregnancy rate and GNP. Disability rate and pregnancy rate are not included in the PQLI. GNP (Gross National Product) is an economic indicator, not a component of the PQLI.
**Option D:** Longevity, Knowledge and Income. While longevity is related to life expectancy, the PQLI uses life expectancy at one year of age specifically. Income is not a direct component of the PQLI, and knowledge is more closely related to literacy rate.

**Clinical Pearl / High-Yield Fact**
The PQLI is often used as a simple, yet effective way to compare the quality of life across different countries, making it a useful tool for policymakers and researchers.

✓ Correct Answer: A. Infant mortality, Life expectancy and Literacy