Given are two statements one is labelled as Assertion A and other is labelled as Reason R.
Assertion A: Magnesium can reduce \( \mathrm{Al_{2}O_{3}} \) at a temperature below \( 1350^{\circ}\mathrm{C} \), while above \( 1350^{\circ}\mathrm{C} \) Aluminium can reduce \( \mathrm{MgO} \).
Reason R: The melting and boiling points of magnesium are lower than those of aluminium.
In light of the above statements, choose most appropriate answer from the options given below: