Question

the reactivity of the metals Al, Ca, Mg and NA follows the order

Answer 1

In the decreasing order of the reactivity, the listed elements could be arranged as follows:-
Na > CA > Mg > Al
The most reactive element here is Sodium and the least reactive element according to this series is Aluminium.

Thanks.

Answer 2

Na | decreasing
Ca. |. reactivity
Mg. l
Al. l