Which of the following are tetrahedral structure?

• A

  ${\left[\mathrm{Ni}{\left(\mathrm{CN}\right)}_4\right]}^{2-}$

• B

  $\left[\mathrm{Ni}{\left(\mathrm{CO}\right)}_4\right]$

• C

  ${\left[{\mathrm{NiCl}}_4\right]}^{2-}$

• D

  ${\mathrm{CrO}}_4^{2-}$