Which of the following elements forms a superoxide when reacted with air?

Given below are two statements:
Statement $I$: The chlorides of $Be$ and $Al$ have $Cl^{-}$-bridged structure. Both are soluble in organic solvents and act as Lewis acids.
Statement $II$: Hydroxides of $Be$ and $Al$ dissolve in excess alkali to give beryllate and aluminate ions.
In the light of the above statements,choose the correct answer from the options given below.

Match the following:

Metal	Ore
$1$. Sodium	$a$. Barite
$2$. Potassium	$b$. Carnallite
$3$. Barium	$c$. Beryl
$4$. Beryllium	$d$. Chile saltpetre

Which one of the following is an oxide?

Which of the following is the most important biological compound containing $Mg$ found in the living world?

$KO_2$ is used in space and submarines because it