For which of the following metal, the carbon reduction cannot be used ?

Options

A. Lead
B. Manganese
C. Tungsten
D. Iron

Answer

To determine which of the following metals cannot be extracted using carbon reduction, we need to analyze the properties of each metal listed: Lead, Magnesium, Tungsten, and Iron.

### Step-by-Step Solution:

1. **Understanding Carbon Reduction**:
- Carbon reduction is a method used to extract metals from their oxides by using carbon as a reducing agent. This process is effective for metals that are less electropositive.

2. **Identifying Electropositivity**:
- Electropositivity refers to the tendency of an element to lose electrons and form positive ions. Metals that are highly electropositive have very stable oxides and are difficult to reduce using carbon.

3. **Analyzing Each Metal**:
- **Lead (Pb)**: Lead is not highly electropositive and can be reduced using carbon.
- **Magnesium (Mg)**: Magnesium is more electropositive than lead, but it can still be reduced using carbon at high temperatures.
- **Tungsten (W)**: Tungsten is a strong electropositive metal, and its oxide is very stable. It forms tungsten carbide when reacted with carbon, making it difficult to reduce by carbon reduction.
- **Iron (Fe)**: Iron can be reduced using carbon, as it is less electropositive compared to tungsten.

4. **Conclusion**:
- Among the given options, Tungsten (W) is the metal for which carbon reduction cannot be effectively used due to its high electropositivity and the stability of its oxide.

### Final Answer:
The correct option is **Tungsten (W)**.