Out of \[{{[Ti{{F}_{6}}]}^{2-}},{{[Co{{F}_{6}}]}^{3-}},C{{u}_{2}}C{{l}_{2}}\] and \[{{[NiC{{l}_{4}}]}^{2-}}\]of (Z of Ti = 22, Co = 27, Cu = 29, Ni = 28), the colourless species are:

• A. \[C{{u}_{2}}C{{l}_{2}}\,\]and \[{{[NiC{{l}_{4}}]}^{2-}}\]
• B. \[{{[Ti{{F}_{6}}]}^{2-}}\] and \[C{{u}_{2}}C{{l}_{2}}\,\]
• C. \[{{[Co{{F}_{6}}]}^{3-}}\] and \[{{[NiC{{l}_{4}}]}^{2-}}\]
• D. \[{{[Ti{{F}_{6}}]}^{2-}}\] and \[{{[Co{{F}_{6}}]}^{3-}}\]