What are some examples of natural sources of air pollution?

Natural sources of air pollution primarily originate from processes that occur in nature without human intervention. Examples such as wildfires release large amounts of smoke and particulate matter into the atmosphere, which can significantly degrade air quality and contribute to respiratory problems in humans and animals. Volcanic eruptions are another significant natural source; they emit sulfur dioxide and ash into the air, which can affect air quality over wide areas and contribute to climate changes. Dust storms can also elevate particulate matter levels, especially in arid regions, and have detrimental effects on human health and the environment.

The other options listed, while they do contribute to air pollution, stem predominantly from human activities. Electric power generation and transportation are tied to combustion processes that release various pollutants, while industrial emissions are a direct result of manufacturing activities. Urban development and farming contribute to pollution mainly through practices that alter land use and contribute to various emissions, such as fertilizers or vehicle exhaust. Thus, the examples in the correct answer reflect purely natural phenomena associated with air pollution, highlighting their significance in understanding the broader context of air quality.