Universal indicator is introduced into a neutral concentrated aqueous sodium chloride solution. This solution contains $\text{H}^+$ (hydrogen), $\text{Na}^+$ (sodium), $\text{Cl}^-$ (chloride) and $\text{OH}^-$ (hydroxide) ions, and is electrolysed. Hydrogen gas is formed at the cathode and chlorine gas is formed at the anode. What change occurs to the colour of the indicator in the solution during electrolysis?
- AThe colour changes from blue to green.
- BThe colour changes from blue to red.
- CThe colour changes from green to blue.
- DThe colour changes from green to red.