**Core Concept**
Proportional Mortality Rate (PMR) is a measure used to calculate the proportion of deaths in a population due to a specific cause. It is expressed as a percentage and represents the proportion of total deaths attributed to a particular disease or cause.

**Why the Correct Answer is Right**
To calculate the PMR from HIV, we need to divide the number of deaths due to HIV (40) by the total number of deaths in the population (200) and multiply by 100 to get the percentage. This gives us the proportion of total deaths in the population that are due to HIV.

PMR = (Number of deaths due to HIV / Total number of deaths) × 100
= (40 / 200) × 100
= 20%

**Why Each Wrong Option is Incorrect**
* **Option A:** This is not a valid option as PMR is always expressed as a percentage and cannot be a decimal value.
* **Option B:** This option is not provided in the question.
* **Option C:** This option is not provided in the question.
* **Option D:** This option is not provided in the question.

**Clinical Pearl / High-Yield Fact**
The PMR is an important metric in epidemiology as it helps to identify the leading causes of death in a population and guides public health interventions.

**Correct Answer:** A. 20%