In addition to carbon dioxide and water vapour, what other gases could have been produced by volcanic activity?

The presence of hydrogen, methane, and ammonia in volcanic gases relates to the conditions of the early Earth and the nature of outgassing during volcanic activity. Early Earth volcanic activity was a significant source of gases that contributed to the primitive atmosphere. In addition to carbon dioxide and water vapor, nitrogen is a major component of the atmosphere today, and it is likely that it was released in large amounts during volcanic eruptions. Small amounts of methane and ammonia could also be released through volcanic processes, especially when organic materials are present or through interactions with water.

This understanding aligns with geological evidence regarding the early atmosphere, which was rich in these gases. Other options presented do not accurately reflect the typical gases associated with volcanic activity or their historical significance in Earth's atmospheric composition.