Which two gases are commonly emitted by volcanoes?

Volcanoes typically emit a mixture of gases, with carbon dioxide and sulfur dioxide being two of the most common. Carbon dioxide is a greenhouse gas that can accumulate in volcanic areas and contribute to various climatic phenomena. When released from a volcano, it can also indicate geological activity. Sulfur dioxide is significant as it can affect air quality and weather patterns. These gases can cause acid rain, contribute to atmospheric changes, and can even impact climate on a larger scale.

While other gases like methane may be present in some volcanic settings, carbon dioxide and sulfur dioxide are quintessentially associated with volcanic eruptions and are studied closely in volcanology for their effects and indicators of volcanic activity. The other options involve gases that are either not emitted in significant quantities by volcanoes or don't represent the typical output associated with volcanic eruptions. Thus, the pairing of carbon dioxide and sulfur dioxide accurately reflects the common volcanic gas emissions.