Which of these statements about ${\left[Co{\left(CN\right)}_6\right]}^{3-}$ is true?

${\left[Co{\left(CN\right)}_6\right]}^{3-}$
$C{o}^{3+}=1s^{2}2s^{2}2p^{2}3s^{2}3p^{2}3d^2$
$C{N}^{-}$ is a strong field ligand and as it approaches the metal ion, the electrons must pair up.
The splitting of the d-orbitals into two sets of orbitals in an octahedral ${\left[Co{\left(CN\right)}_6\right)}^{3-}$ may be represented as

Here, for $d^6$ ions, three electrons first enter orbitals with parallel spin put the remammg may pair up in $t_{2g}$ orbital giving rise to low spin complex (strong ligand) field.
$\therefore {\left[Co{\left(CN\right)}_6\right]}^{3-}$ has no unpaired electron and will be in a low spin configuration.