A: Beryllium chloride has much lower electrical conductivity than calcium and  magnesium chlorides (salts are exist in fused state)
R : Beryllium exists as  ${\left[Be{\left(H_{2}O\right)}_4\right]}^{++}$ in acid medium and ${\left[Be{\left(OH\right)}_4\right]}^{-}$  in basic medium

$BeC{l}_2$  is covalent compound  $CaC{l}_2\&MgC{l}_2$ is ionic compound
${\left[Be{\left(H_{2}O\right)}_4\right]}^{2+}$   is an acid. The hydrated beryllium ions is are strongly acidic. The small beryllium ion centre attracts at the electrons in the bonds towards itself and that makes the hydrogen atoms in the water even more positive than the usually rare.