The correct statements with respect to Ellingham’s diagram among the following are

I) Magnesium reduces aluminium oxide below 1700K

II) Aluminium reduces magnesium oxide above 1700K

III) Aluminium reduces magnesium oxide below 1700K

IV) Magnesium reduces aluminium oxide above 1700K

(I) Magnesium reduces aluminum oxide below 1700 K.

Below 1700 K, $\Delta \mathrm{G}°$ for the reaction $2\mathrm{Mg}+{\mathrm{O}}_2\to 2\mathrm{MgO}$ is more negative than$\Delta \mathrm{G}°$ for the reaction  $\mathrm{\Delta G}°$

$\frac{4}{3}\mathrm{Al}+{\mathrm{O}}_2\to \frac{2}{3}{\mathrm{Al}}_2{\mathrm{O}}_3$

(II) Aluminium reduces magnesium oxide above 1700 K

Above 1700 K, $\Delta \mathrm{G}°$ for the reaction $2\mathrm{Mg}+{\mathrm{O}}_2\to 2\mathrm{MgO}$ is less  negative than $\mathrm{\Delta G}°$ for the reaction  

$\frac{4}{3}\mathrm{Al}+{\mathrm{O}}_2\to \frac{2}{3}{\mathrm{Al}}_2{\mathrm{O}}_3$

The more negative the value of $\Delta \mathrm{G}°$, the greater is the tendency of the element to combine with oxygen.

Therefore, Option A is the correct answer.