| 1. | Above 1350°C, Mg can reduce Al2O3 and below1350°C, Al can reduce MgO | 
| 2. | Mg can reduce Al2O3 and Al can reduce MgO above 1350°C | 
| 3. | Mg can reduce Al2O3 and Al can reduce MgO below 1350°C | 
| 4. | Below 1350°C, Mg can reduce Al2O3 and above 1350°C, Al can reduce MgO |