Introduction:
The Human Development Index (HDI) is a composite measure that assesses the overall progress of a country in various dimensions. It provides a holistic view of a country's development by considering multiple indicators in three key dimensions - health, education, and income.

Explanation:
The correct answer is option 'A' - Health, Education, Income. Let's explore each dimension in detail:

Health:
Health is one of the core dimensions of HDI. It reflects the overall well-being and longevity of a country's population. The health dimension considers various indicators such as life expectancy at birth, mortality rates, access to healthcare services, and disease prevalence. These indicators help assess the overall health status and healthcare infrastructure of a nation.

Education:
Education is another crucial dimension of HDI. It focuses on the level of knowledge and skills acquired by the population. The education dimension takes into account indicators such as literacy rates, school enrollment ratios, and the quality of education. These indicators help evaluate a country's investment in education and its ability to provide equitable access to educational opportunities.

Income:
The income dimension of HDI measures the standard of living and economic well-being of a country's population. It considers indicators such as Gross National Income (GNI) per capita and the level of income inequality. The income dimension reflects the distribution of wealth and economic opportunities within a society.

Conclusion:
The Human Development Index (HDI) encompasses three key dimensions - health, education, and income. By considering indicators from these dimensions, HDI provides a comprehensive assessment of a country's overall progress and development. It helps policymakers and researchers understand the areas where a country is excelling and where it needs to focus its efforts for improvement.