Which of the following alkaline-earth metal hydroxides is the strongest base?

Bleaching powder is obtained by passing chlorine on

Match the following alkaline earth metals with their respective densities $(g/cm^3)$:

$A$. $Be$	$I$. $1.74$
$B$. $Mg$	$II$. $1.84$
$C$. $Ca$	$III$. $2.63$
$D$. $Sr$	$IV$. $1.55$

Identify the correct statements with respect to compounds of Beryllium:
$I$. Beryllium oxide is amphoteric in nature.
$II$. Beryllium hydride is formed by the reaction of beryllium with hydrogen.
$III$. Beryllium hydride is formed by the reaction of beryllium chloride with lithium aluminium hydride.
$IV$. Beryllium sulphate is the least soluble sulphate among the sulphates of alkaline earth metals.

Group $2$ hydrides with significant covalent character is/are:

$X$-ray tube windows are made using which of the following metals?