Question

what is the greatest source of indoor air pollution in less-developed countries? air conditioning units poorly ventilated cooking fires

Explanation:

In less - developed countries, many households use traditional cooking methods with fires (like wood - burning stoves) that are poorly ventilated. These fires release pollutants such as particulate matter, carbon monoxide, and other harmful gases into the indoor air. Air - conditioning units are not as common in less - developed countries as a source of indoor air pollution, and their pollution contribution is much less compared to poorly ventilated cooking fires.

Answer:

Poorly ventilated cooking fires