Identify the correct statement among the following.
a) Solubility of alkaline earth metal hydrides in water increases down the group
b) Thermal decomposition of (NH₄)₂ BeF₄ gives BeF₂
c) In the vapour phase BeCl₂ tends to form dimer
d) Hydride of calcium is also called hydrolith
 

Down the group the lattice energies of alkali metal hydroxides decrease due to the increase in atomic size. Further down the group ionic character of these hydroxide increases due to increase in electropositive character. So the solubilities increase.

(NH₄)₂BeF₄⟶2NH₄F+BeF₂

In the vapour phase BeCl₂ tends to form a chloro-bridged dimer which dissociates into the linear monomer at high temperatures of the order of 1200 K.

Hydrolith is basically a salt-like binary compound having the chemical formula CaH₂.