The geometry of ${\left[\mathrm{Co}(\mathrm{CO}{)}_4\right]}^{-}$ and ${\left[\mathrm{Cd}(\mathrm{CN}{)}_4\right]}^{2-}$ are :

Since central atom in ${\left[\mathrm{Co}(\mathrm{CO}{)}_4\right]}^{-}$ and ${\left[\mathrm{Cd}(\mathrm{CN}{)}_4\right]}^{2-}$ is located at the center with four substituents that are located at the corners of a tetrahedron. They are tetrahedral in structure.

Hence correct option is B.