**Core Concept**
The best parameter to measure air pollution involves assessing the concentration of pollutants in the air, which can have significant effects on human health and the environment. Air pollution can be measured in terms of various parameters such as particulate matter (PM), nitrogen dioxide (NO2), ozone (O3), and sulfur dioxide (SO2).

**Why the Correct Answer is Right**
The most commonly used parameter to measure air pollution is particulate matter (PM), specifically PM2.5 and PM10. PM2.5 refers to particles with a diameter of 2.5 micrometers or less, while PM10 refers to particles with a diameter of 10 micrometers or less. These particles can be inhaled deep into the lungs and cause respiratory problems. The World Health Organization (WHO) recommends monitoring PM2.5 concentrations to assess air quality and protect public health.

**Why Each Wrong Option is Incorrect**
* **Option A:** Not a commonly used parameter for measuring air pollution.
* **Option B:** While nitrogen dioxide (NO2) is a pollutant, it is not the best parameter to measure air pollution due to its limited scope compared to particulate matter.
* **Option C:** Ozone (O3) is a pollutant, but its concentration is not the best indicator of overall air quality.
* **Option D:** Sulfur dioxide (SO2) is a pollutant, but its concentration is not the best parameter to measure air pollution due to its limited scope compared to particulate matter.

**Clinical Pearl / High-Yield Fact**
The Air Quality Index (AQI) is a widely used tool to communicate air quality to the public and protect public health. It is based on the concentration of PM2.5 and other pollutants in the air.

**Correct Answer: C. Ozone (O3).**