Final answer:
The existence of the carbon dioxide (CO₂) cycle on Earth is dependent on life and active volcanism.
Step-by-step explanation:
The two critical factors for the existence of the carbon dioxide (CO₂) cycle on Earth are life and active volcanism. Life, specifically plants and algae, play a vital role in this cycle through photosynthesis, where they absorb carbon dioxide from the atmosphere and release oxygen. Active volcanism releases carbon dioxide into the atmosphere through volcanic eruptions.
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