Correct Answer - D
The compounds having metal ions with unpaired electrons, are coloured. Thus, in `TiCl_(3)`
`Ti^(3+) = [Ar]3d^(1) (` one unpaired electron ) in `FeCl_(3)`
`Fe^(3+)= [Ar]3d^(5) (` Five unpaired electrons)in `CoCl_(2)`
`Co^(2+) = [Ar]3d^(7)` ( Three unpaired electrons )
Hence, all compounds are coloured.