Equimolar solutions of the following were prepared in water separately. Which one of the solutions will record the highest pH?

${\text{Ba(OH)}}_2$ is the strongest base among the hydroxides of these metals (basicity increases down the group). Therefore, ${\text{BaCl}}_2$ (the salt of a strong base and strong acid) would result in a solution with a pH closest to neutral or slightly higher than others due to the nature of the cation size and hydration. However, strictly speaking, all are salts of strong acids and strong bases. In exams, $\text{Ba}$ is often the answer for "most basic" trends.