Which chemical process primarily causes sulfur dioxide emissions?

Sulfur dioxide emissions are primarily generated through the combustion of fossil fuels. When fossil fuels like coal, oil, or natural gas are burned for energy, they undergo a chemical reaction that releases various gases, including sulfur dioxide. This occurs because many fossil fuels contain sulfur compounds, which oxidize during combustion and produce sulfur dioxide as a byproduct.

The other options do not significantly contribute to sulfur dioxide emissions. Photosynthesis is a natural process by which plants convert carbon dioxide and sunlight into oxygen and glucose, and it does not produce sulfur dioxide. Electrolysis is a method used to separate compounds into their elements or simpler compounds using electricity, which does not lead to the release of sulfur dioxide. Filtration is a physical separation process and does not involve any chemical reactions that would result in sulfur dioxide emissions. Thus, the combustion of fossil fuels is the primary driver of sulfur dioxide emissions due to the inherent sulfur content in the fuels used.