An element A belonging to group 2 and period 2 reacts with chlorine at elevated temperature to give compound (B) compound B combines with `LiAlH_4` to form compound (C). Which is an hydride identify A, B and C.

Explanation

(i) An element A belonging to II group and II period is beryllium (A)
(ii) Beryllium reacts with chlorine to form beryllium chloride (B).
`Be+Cl_2tounderset((B))BeCl_2`
(iii) Beryllium chloride on treatment with `LiAlH_4` forms beryllium hydride (C)
`2BeCl_2+LiAlH_4tounderset((C))2BeH_2+LiCl+AlCl_3`