**Core Concept**
The Human Poverty Index-1 (HPI-1) is a composite measure used to assess the deprivation of basic needs in a population, focusing on three dimensions: a long and unhealthy life, being unable to achieve a satisfactory level of education, and a lack of a decent standard of living. The HPI-1 is a weighted average of three indicators: probability at birth of not surviving to age 40, expected years of schooling, and adult literacy rate.

**Why the Correct Answer is Right**
The HPI-1 excludes the percentage of the population not using an improved water source, which is a critical indicator of a decent standard of living. The correct answer focuses on the calculation of HPI-1, which specifically excludes this indicator. The other indicators included in the HPI-1 calculation are the probability at birth of not surviving to age 40 (which reflects a long and unhealthy life), expected years of schooling (which reflects a satisfactory level of education), and adult literacy rate (which also reflects a satisfactory level of education).

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided, but if it were an indicator of a long and unhealthy life, it might be included in the HPI-1 calculation.
**Option B:** Expected years of schooling is a key indicator of a satisfactory level of education, so it would be included in the HPI-1 calculation.
**Option C:** Adult literacy rate is another critical indicator of a satisfactory level of education, so it would be included in the HPI-1 calculation.
**Option D:** This option is not provided, but if it were an indicator of a decent standard of living, it might be included in the HPI-1 calculation.

**Clinical Pearl / High-Yield Fact**
The HPI-1 is a useful tool for policymakers and researchers to assess the deprivation of basic needs in a population. It highlights the importance of addressing the root causes of poverty and deprivation to improve human development outcomes.

**Correct Answer: D.**