Name one substance which undergoes spontaneous combustion (or burns in air at room temperature).

Explanation

**Step-by-Step Solution:**

1. **Understanding Spontaneous Combustion:**
- Spontaneous combustion refers to the process where a substance ignites and burns without an external ignition source, simply due to the heat generated from chemical reactions within the substance itself.

2. **Identifying a Substance:**
- We need to identify a substance that can spontaneously combust at room temperature.

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