$KO_2$ is used in space and submarines because it

$P \xrightarrow{\Delta } Q$ (metallic solid) $+ R \uparrow + S \uparrow$
$X \xrightarrow{\Delta } Y$ (amphoteric oxide) $+ R \uparrow + S \uparrow$
$P$ and $X$ are respectively:

Sodium metal cannot be stored under

Select the incorrect statement.

Which of the following metals is not found in the free state?

Choose the correct statement from the following.