# Hydrolith a source of hydrogen is

$\begin{array}{1 1}(a)\;NaH\\(b)\;CaH_2\\(c)\;LiH\\(d)\;BaH_2\end{array}$

$CaH_2$ is called hydrolith.
The formula for this chemical compound is $CaH_2$.
this compound was available as a hydrogen source under the trade-name of “Hydrolith”. It has been used as a source of hydrogen for a very long time. It is still used for producing pure hydrogen in laboratories for various experiments.
Hence (b) is the correct answer.
edited Nov 25, 2017