The correct order of the wavelength of light absorbed by the following complexes is,A. $[\text{Co}({\text{NH}}_3{)}_6{]}^{3+}$ B. $[\text{Co}(\text{CN}{)}_6{]}^{3-}$ C. $[\text{Cu}({\text{H}}_2\text{O}{)}_4{]}^{2+}$ D. $[\text{Ti}({\text{H}}_2\text{O}{)}_6{]}^{3+}$ Choose the correct answer from the options given below:

Wavelength of light absorbed ($\lambda$) is inversely proportional to the crystal field splitting energy ($\Delta$), which depends on the field strength of the ligands.Field strength order: ${\text{CN}}^{-}>{\text{NH}}_3>{\text{H}}_2\text{O}$.For the same metal (Co), $[\text{Co}(\text{CN}{)}_6{]}^{3-}$ (B) has a higher $\Delta$ and thus a lower $\lambda$ than $[\text{Co}({\text{NH}}_3{)}_6{]}^{3+}$ (A). So, $\text{B}<\text{A}$.For aqua complexes, ${\text{Ti}}^{3+}$ (D) has a higher oxidation state and splitting than ${\text{Cu}}^{2+}$ (C).Considering the metal ion and ligand strength together, the order of increasing wavelength is $\text{B}<\text{A}<\text{D}<\text{C}$.