What gases were primarily released by volcanic activity that contributed to the formation of the Earth's early atmosphere?

Volcanic activity primarily released carbon dioxide, water vapour, and nitrogen, which contributed to the formation of the Earth's early atmosphere.

A strong answer should directly address the approved learning objective to explain that volcanic activity released gases that formed the early atmosphere. This question belongs to The Earth's early atmosphere within The composition and evolution of the Earth's atmosphere, so the response should use that exact curriculum context rather than a generic statement. The answer is correct when it names the key idea, explains the link to early atmosphere, and keeps the wording specific to AQA GCSE revision.