Among the following alkaline earth metal halides, one which is covalent and soluble in organic solvents is:

According to Fajan's rule, a smaller cation with high charge density has more polarizing power and thus more covalent character. ${\text{Be}}^{2+}$ is the smallest cation among the alkaline earth metals. Due to its very small size and high polarizing power, ${\text{BeCl}}_2$ is essentially covalent and dissolves in organic solvents like ethanol or ether.