Hydrogen readily combines with metals and thus shows its

$BeH_2$ can be prepared by the reaction of

Calcium imide on hydrolysis gives gas $(B)$ which on oxidation by bleaching powder gives gas $(C)$. Gas $(C)$ on reaction with magnesium gives compound $(D)$ which on hydrolysis again gives gas $(B)$. Identify $(B)$,$(C)$ and $(D)$.

$A$ deuteron contains

Arrange the following:
$(i)$ $CaH_{2}$,$BeH_{2}$,and $TiH_{2}$ in order of increasing electrical conductance.
$(ii)$ $LiH$,$NaH$,and $CsH$ in order of increasing ionic character.
$(iii)$ $H-H$,$D-D$,and $F-F$ in order of increasing bond dissociation enthalpy.
$(iv)$ $NaH$,$MgH_{2}$,and $H_{2}O$ in order of increasing reducing property.

Which of the following reactions produces hydrogen?