A few drops of thymolphthalein and methyl orange are each added separately to two test-tubes that contain solution X. Next, solution Y is added to both test-tubes until it is in excess. The indicator colours before and after the addition of solution Y are shown. What is solution Y?
- A$\mathrm{HCl(aq)}$
- B$\mathrm{NaOH(aq)}$
- C$\mathrm{H_2O(l)}$
- D$\mathrm{NaCl(aq)}$