Below `1623 K, Al` can reduce `MgO` to `Mg`, but above `1623 K`, reverse is true.

Answer

F

Explanation

Below `1623 K`, the `Delta_(f) G^(Ө)` of `MgO` is lower than that of `Al_(2)O_(3)` and hence `Mg` can reduce `Al_(2)O_(3)` to `Al` , but above `1623 K, Delta_(f) G^(Ө)` of `Al_(2)O_(3)` is lower than that of `MgO` and hence `Al` can reduce `MgO` to `Mg`.