Hall-Heroult's process is given by :

Options

A. (A)`2Al_(2)O_(3)+3Cto4Al+3CO_(2)`
B. (B)`Cr_(2)O_(3)+2AltoAl_(2)O_(3)+2Cr`
C. (C)`Cu^(2)+(aq)+H_(2)(g)toCu(s)+2H^(+)(aq)`
D. (D)`ZnO+Coverset("Coke,1673K")toZn+CO`

Explanation

### Step-by-Step Solution:

1. **Understanding the Hall-Heroult Process**:
- The Hall-Heroult process is an industrial method for extracting aluminum from its ore, primarily bauxite (Al₂O₃).

2. **Chemical Reactions Involved**:
- The overall reaction for the Hall-Heroult process can be summarized as follows:
\[ 2 \text{Al}_2\text{O}_3 + 3 \text{C} \rightarrow 4 \text{Al} + 3 \text{CO}_2 \]
- This reaction indicates that aluminum oxide reacts with carbon to produce aluminum and carbon dioxide.

3. **Reactions at the Electrodes**:
- At the **cathode** (negative electrode), the reduction reaction occurs:
\[ 4 \text{Al}^{3+} + 12 \text{e}^- \rightarrow 4 \text{Al (l)} \]
- This shows that aluminum ions gain electrons to form liquid aluminum.

- At the **anode** (positive electrode), the oxidation reaction occurs:
\[ 6 \text{O}^{2-} \rightarrow 3 \text{O}_2 + 12 \text{e}^- \]
- This indicates that oxide ions lose electrons to form oxygen gas.

4. **Combustion of Carbon**:
- Additionally, the carbon used in the process reacts with the oxygen produced:
\[ 3 \text{C} + 3 \text{O}_2 \rightarrow 3 \text{CO}_2 \]
- This reaction shows that carbon reacts with oxygen to produce carbon dioxide.

5. **Conclusion**:
- The Hall-Heroult process is crucial for the extraction of aluminum, and the reactions at the electrodes and the overall reaction highlight the chemical transformations involved.

### Final Answer:
The Hall-Heroult process is primarily used for smelting aluminum.