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

• A
  Both $A$ and $R$ are correct,and $R$ is the correct explanation of $A$.
• B
  Both $A$ and $R$ are correct,but $R$ is $NOT$ the correct explanation of $A$.
• C
  $A$ is correct,$R$ is not correct.
• D
  $A$ is not correct,$R$ is correct.