Step 1: Understanding the Concept:
\(sp^3d^2\) hybridisation gives outer orbital (high spin) octahedral complexes. Weak field ligands (F\(^-\)) cause this.
Step 2: Detailed Explanation:
(A) Co\(^{3+}\) in [CoF\(_6\)]\(^{3-}\): F\(^-\) is weak field ligand, so electrons do not pair, hybridisation = \(sp^3d^2\) (outer orbital).
(B) [Co(NH\(_3\))\(_6\)]\(^{3+}\): NH\(_3\) is strong field, hybridisation = \(d^2sp^3\) (inner orbital).
(C) [Fe(CN)\(_6\)]\(^{3-}\): CN\(^-\) is strong field, hybridisation = \(d^2sp^3\).
(D) [Cr(NH\(_3\))\(_6\)]\(^{3+}\): NH\(_3\) is strong field for Cr\(^{3+}\), hybridisation = \(d^2sp^3\).
Step 3: Final Answer:
\([\mathrm{CoF}_6]^{3-}\)