$2Na+H_2\quad\underrightarrow{heat}\quad 2NaH$,$Ca+H_2\rightarrow CaH_2$,$2Li+H_2\rightarrow x$.Then $x$ is

Question

$\begin{array}{1 1}(a)\;LiH_2\\(b)\;LiH_3\\(c)\;2LiH\\(d)\;LiH\end{array}$