Which of the following are natural sources of sulfur in the atmosphere?

Natural sources of sulfur in the atmosphere include volcanic eruptions and hot springs. These natural phenomena release sulfur compounds, such as sulfur dioxide (SO2), into the air as a result of geological processes. When volcanoes erupt, they can emit large quantities of gases, including sulfur, which can contribute to atmospheric sulfur levels and influence climate and air quality. Hot springs also can release dissolved gases, including sulfur gases, contributing to the overall sulfur content in the atmosphere.

In contrast, the other options represent anthropogenic, or human-made, sources of sulfur emissions. Manufacturing processes, coal burning, and waste disposal are all activities that result in the release of sulfur into the atmosphere primarily as a by-product of industrial activities. These sources, while significant contributors to sulfur pollution, are not considered natural. Thus, the correct answer highlights a natural phenomenon that directly contributes to sulfur presence in the atmosphere.