Identify the reaction mentioned

The question says that compound $X$ reacts with phthalic anhydride in presence of concentrated $\mathrm{H_2SO_4}$ to give $Y$, and $Y$ is used as an acid-base indicator.

Recall the standard preparation of common indicators

Phenolphthalein is prepared by condensation of phenol (also called carbolic acid) with phthalic anhydride in presence of concentrated sulfuric acid.

The reaction is: $\text{Phenol} + \text{Phthalic anhydride} \xrightarrow[\ ]{\mathrm{conc.\ H_2SO_4}} \text{Phenolphthalein}$

Match with the options

• A: Toludine, Phenolphthalein
  Toluidine is an aromatic amine, not the standard reactant for preparing phenolphthalein. So this is incorrect.

• B: Carbolic acid, Phenolphthalein
  Carbolic acid is another name for phenol. Phenol reacts with phthalic anhydride to form phenolphthalein, which is an acid-base indicator. So this is correct.

• C: Salicylaldehyde, Phenolphthalein
  Salicylaldehyde does not give phenolphthalein in this reaction. Incorrect.

• D: Anisole, methyl orange
  Methyl orange is an azo dye indicator, not formed by reacting anisole with phthalic anhydride. Incorrect.

Conclusion

Therefore, $X = \text{Carbolic acid (phenol)}, \quad Y = \text{Phenolphthalein}$

So the correct option is B.