Explanation:

- Option 1: Ringworm

- Ringworm is a skin infection caused by a fungus. It's characterized by red, itchy patches that form a ring-like appearance.

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- Option 2: Diarrhoea

- Diarrhoea is usually caused by bacterial or viral infections, not fungus. It's characterized by loose, watery stools.

- Option 3: Smallpox

- Smallpox is caused by the variola virus. It's a contagious disease that's been eradicated through vaccination.

- Option 4: Polio

- Polio is a viral disease that can affect nerves and lead to partial or full paralysis.

So, Ringworm is indeed the correct answer, as it's the only option caused by a fungus.