___________is used as a reducing agent in the extraction of metals from their respective metallic oxides.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a substance that is used as a reducing agent in the extraction of metals from their respective metallic oxides.

2. **Identifying Reducing Agents**: A reducing agent is a substance that donates electrons to another substance, reducing its oxidation state. In metallurgy, reducing agents are used to convert metal oxides into pure metals.

3. **Common Reducing Agents**: One of the most common reducing agents used in the extraction of metals from their oxides is carbon, particularly in the form of wood charcoal.

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