**Core Concept**
The Human Poverty Index (HPI) is a measure used to determine the deprivation in basic dimensions of human development, including life expectancy at birth, expected years of schooling, and the proportion of people without sustainable access to an improved water source.

**Why the Correct Answer is Right**
The HPI is a composite index that takes into account three basic dimensions of human development: a long and healthy life, knowledge, and a decent standard of living. It uses a combination of indicators such as life expectancy at birth, expected years of schooling, and the proportion of people without access to basic necessities like clean water and sanitation. This index provides a comprehensive picture of deprivation in human development, making it a crucial tool for policymakers and researchers.

**Why Each Wrong Option is Incorrect**
**Option B:** The Human Development Index (HDI) is a related concept, but it measures the average achievement in three basic dimensions of human development: life expectancy, expected years of schooling, and Gross National Income (GNI) per capita. While it does provide a broader picture of human development, it does not specifically focus on deprivation.
**Option C:** The Physical Quality of Life Index (PQLI) is an alternative measure of human development, but it focuses on three basic indicators: literacy rate, infant mortality rate, and life expectancy at age one. It does not capture the same level of deprivation as the HPI.
**Option D:** The Development Deprivation Index is not a recognized term in the field of human development, making it an incorrect choice.

**Clinical Pearl / High-Yield Fact**
The HPI is an important tool for policymakers and researchers to identify areas of deprivation in human development and to track progress towards achieving the United Nations' Millennium Development Goals (MDGs) and the Sustainable Development Goals (SDGs).

**✓ Correct Answer: A. Human povey index**