Which substance is formed when aluminium reacts with oxygen?

The correct option is A

${Al}_2{O}_3$

Aluminium reacts with oxygen present in the air to form aluminium oxide. The reaction involved is:

$4Al\left(s\right)$ + $3O_2\left(g\right)$ $\to$ $2{Al}_2{O}_3\left(s\right)$

Aluminium oxide is a protective layer formed on the aluminium body which prevents further oxidation of aluminium.