When hydrochloric acid is added to cobalt nitrate solution at 'room temperature, the following reaction takes place and the solution turns blue.

$$\begin{gathered} {\left[\mathrm{Co}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+}\left(aq\right)+4{\mathrm{Cl}}^{-}\left(aq\right)\to {\left[{\mathrm{CoCl}}_4\right]}^{2-}\left(aq\right)+6{\mathrm{H}}_2\mathrm{O}\left(l\right) \\ \mathrm{pink} \mathrm{Blue} \end{gathered}$$

However when cooled to a temperature below room temperature, the solution turns pink. On the basis of this information mark the appropriate option: