Co NH 3 6 3 + and CoF 6 3 - are respectively known as:

In the complex ${\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]}^{3+}$ Ammonia is strong field ligand and electronic configuration of 

${\mathrm{Co}}^{3+}$$\Rightarrow 3 {\mathrm{d}}^6\left({\mathrm{t}}_{2 \mathrm{g}}^6,{\mathrm{e}}_{\mathrm{g}}^0\right)$

Hybridisation: ${\mathrm{d}}^2{\mathrm{sp}}^3$

Pairing of electrons takes place due to the strong field ligand. Hence, it is inner orbital complex (spin paired complex).

In the complex ${\left[{\mathrm{CoF}}_6\right]}^{3-}$ fluoride is weak field ligand and electronic configuration of  ${\mathrm{Co}}^{3+}$ $\Rightarrow 3{\mathrm{d}}^6\left({\mathrm{t}}_{2\mathrm{g}}^4,{\mathrm{e}}_{\mathrm{g}}^2\right)$.

Hybridisation: ${\mathrm{sp}}^3{\mathrm{d}}^2$

Pairing of electrons not takes place due to the weak field ligand. Hence, it is outer orbital complex (spin free complex).

Hence option B is the answer.