Which gas was likely NOT a major part of the Earth's first atmosphere?

Name: Which gas was likely NOT a major part of the Earth's first atmosphere?
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Question

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Oxygen was not a major part of Earth's first atmosphere. The early atmosphere was primarily composed of gases like hydrogen, helium, methane, and ammonia, released from volcanic activity. Oxygen levels increased significantly later, primarily due to photosynthetic organisms.

Which Gas Was Likely NOT a Major Part of the Earth's