If $\Delta$₀ < P , the correct electronic configuration for d⁴ system will be

Crystal field theory for ${\mathrm{d}}^4$ configuration.

Because of the weak field ligand with metal, it is a high spin complex if $\Delta$₀ < P.

In one of the e_g orbitals fourth electron enters.

Crystal field theory (so Ligand field theory) is the creation of Alfred Werner. Also, it is called the Landé g factor. Crystal field theory explains how a d orbital interacts with metal ions and how much electrons are shifted away from each other. 

Its strength depends on the ligand field case of the ligands that are attached to the metal ion, then complexes are classified in terms of their configuration in terms of high or low spin.

Hence, the correct answer is option (C).