(a) Universal indicator is a mixture of many different indicators which gives different colours at different $\mathrm{pH}$ values of the entire $\mathrm{pH}$ scale. It shows different colours at different concentrations of hydrogen ions in a solution. (b) Solution A gives pink colour when a drop of phenolphthalein indicator is added, therefore A is a base.Solution B gives red colour when a drop of methyl orange is added to it, therefore $B$ is an acid.Hence, solution A will have less concentration of hydrogen ion than $B$.Thus, A will have $\mathrm{pH}$ more than 7 beause $\mathrm{pH}$ value of(i) an acid solution $< 7$(ii) a base solution $>7$(iii) a neutral solution $=7$(c) (i) The salts of strong acids and weak bases give acidic solution having $\mathrm{pH}$ less than 7. Example, $\mathrm{NH}_4\mathrm{Cl}$, Ammonium Chloride will have $\mathrm{pH}$ less than 7.(ii) The salts of weak acids and strong bases give basic solution having pH more than 7. Example, $\mathrm{Na}_2\mathrm{CO}_3$ Sodium Carbonate will have $\mathrm{pH}$ more than 7 .