a
\(\mathrm{BaCl}_{2}\) is a salt of strong acid \(HCl\) and strong base \(\mathrm{Ba}(\mathrm{OH})_{2}\). So, its aqueous solution is neutral with \(pH\). All other salts give acidic solution due to cationic hydrolysis, so their \(pH\) is less than \(7\). Thus, \(pH\) value is highest for the solution of \(BaCl_2\)