The pH of 0.1 M solution of the following salts increases in the order :

${\mathrm{NH}}_4 \mathrm{Cl}$ is acidic while $\mathrm{NaCN}$ is basic. So, the pH of 0.1 M solution of the salts increases in the order :

$\mathrm{HCl}<{\mathrm{NH}}_4\mathrm{Cl}<\mathrm{NaCl}<\mathrm{NaCN}$