In the metallurgy of aluminium,

Options

A. `Al^(3+)` is oxidised to `Al_((s))`
B. graphite anode is oxidised to carbon monoxide and carbon dioxide.
C. oxidation state of oxygen changes in the reaction at anode
D. oxidation state of oxygen change in the overall reaction involved in the process.

Explanation

### Step-by-Step Solution:

1. **Understanding the Process**: The metallurgy of aluminum primarily involves the Hall-Héroult process, where aluminum oxide (Al₂O₃) is reduced to aluminum metal. This process requires an electrolytic cell.

2. **Components of the Electrolytic Cell**: In the Hall-Héroult process, the main components include:
- **Electrolyte**: A mixture of Al₂O₃ and a flux like Na₃AlF₆ or CaF₂, which lowers the melting point and increases conductivity.
- **Electrodes**: A carbon cathode and a graphite anode.

3. **Reactions at the Electrodes**:
- **At the Cathode**: Aluminum ions (Al³⁺) are reduced to aluminum metal (Al).
\[ \text{Al}^{3+} + 3e^- \rightarrow \text{Al (s)} \]
- **At the Anode**: The carbon anode is oxidized, producing carbon monoxide (CO) and carbon dioxide (CO₂).
\[ \text{C (s)} + 2\text{O}^{2-} \rightarrow \text{CO (g)} + 2\text{O}^{2-} \]
\[ \text{C (s)} + \text{O}^{2-} \rightarrow \text{CO}_2 (g) + 4\text{e}^- \]

4. **Analyzing the Options**:
- **Option 1**: "Al³⁺ is oxidized to aluminum solid." This is incorrect because Al³⁺ is reduced, not oxidized.
- **Option 2**: "Graphite anode is oxidized to carbon monoxide and carbon dioxide." This is correct as the anode undergoes oxidation.
- **Option 3**: "Oxidation state of oxygen changes in the reaction at the anode." This is incorrect; the oxidation state of oxygen remains -2 in both CO and CO₂.
- **Option 4**: "Oxidation state of oxygen changes in the overall reaction involved in the process." This is also incorrect for the same reason as option 3.

5. **Conclusion**: The only correct statement is option 2. Therefore, the answer is that the graphite anode is oxidized to carbon monoxide and carbon dioxide.