The correct answer is C. both a and b.
Air pollution can be of natural origin, such as from volcanoes, forest fires, and dust storms. It can also be of artificial or man-made origin, such as from burning fossil fuels, industrial emissions, and vehicle exhaust.
Natural air pollution can be a major problem in some parts of the world, especially in areas with active volcanoes or frequent forest fires. However, artificial air pollution is a much larger problem, as it is caused by human activities that are widespread and ongoing.
Artificial air pollution can cause a variety of health problems, including respiratory problems, heart disease, and cancer. It can also damage crops and ecosystems.
There are a number of things that can be done to reduce air pollution, such as investing in renewable energy sources, improving energy efficiency, and using cleaner transportation fuels.