How many of these metals carbon reduction is used during their extraction.
`Ag, Au, Fe, Sn, Zn, Pb, Al`

Answer

To determine how many of the given metals use carbon reduction during their extraction, we will analyze each metal one by one:

1. **Silver (Ag)**: Silver is extracted using the MacArthur cyanide process, which does not involve carbon reduction. Therefore, Ag does not count.

2. **Gold (Au)**: Similar to silver, gold is also extracted using the MacArthur cyanide process, which does not involve carbon reduction. Therefore, Au does not count.

3. **Iron (Fe)**: Iron is extracted from its ore (Fe2O3) using carbon reduction. The reaction can be represented as:
\[ \text{Fe}_2\text{O}_3 + 3\text{C} \rightarrow 2\text{Fe} + 3\text{CO} \]
Thus, Fe counts.

4. **Tin (Sn)**: Tin is extracted from its oxide (SnO2) using carbon reduction. The reaction can be represented as:
\[ \text{SnO}_2 + 2\text{C} \rightarrow \text{Sn} + 2\text{CO} \]
Thus, Sn counts.

5. **Zinc (Zn)**: Zinc is extracted from its oxide (ZnO) using carbon reduction. The reaction can be represented as:
\[ \text{ZnO} + \text{C} \rightarrow \text{Zn} + \text{CO} \]
Thus, Zn counts.

6. **Lead (Pb)**: Lead is extracted from its oxide (PbO) using carbon reduction. The reaction can be represented as:
\[ \text{PbO} + \text{C} \rightarrow \text{Pb} + \text{CO} \]
Thus, Pb counts.

7. **Aluminum (Al)**: Aluminum is extracted using the Hall-Héroult process, which involves electrolysis rather than carbon reduction. Therefore, Al does not count.

Now, we can summarize the metals that use carbon reduction during their extraction:
- Iron (Fe)
- Tin (Sn)
- Zinc (Zn)
- Lead (Pb)

Therefore, the total number of metals that use carbon reduction in their extraction is **4**.

### Final Answer:
**4 metals (Fe, Sn, Zn, Pb) use carbon reduction during their extraction.**