Explanation:

- Carbon forms the greatest number of compounds due to its ability to form stable covalent bonds with many elements, including itself, leading to an immense diversity of organic compounds.

- Oxygen is crucial in forming oxides, acids, and alcohols, but fewer compounds compared to carbon.

- Nitrogen, while essential in forming amines and nitrides, also doesn't surpass carbon in compound diversity.

- Hydrogen forms numerous compounds, particularly with carbon and other non-metals, but not as diverse as carbon's.

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