Read the passage carefully and answer.

The crystal field theory (CFT) is an electrostatic model which considers the metal-ligand bond to be ionic arising purely from electrostatic interactions between the metal ion and the ligand. Ligands are treated as point charges in case of anions or dipoles in case of neutral molecules. The five d orbitals in an isolated gaseous metal atom/ion have same energy, i.e., they are degenerate. This degeneracy is maintained if a spherically symmetrical field of negative charges surrounds the metal atom/ion. However, when this negative field is due to ligands (either anions or the negative ends of dipolar molecules like $NH_3$ and $H_2O$) in a complex, it becomes asymmetrical and the degeneracy of the d orbitals is lifted. It results in splitting of the d orbitals. The pattern of splitting depends upon the nature of the crystal field.

If the fourth electron in d subshell enters one of the $e_g$ orbitals in octahedral complexes, it indicates that

the ligand is weak, and forms high spin complexes.

The correct answer is Option (2) → the ligand is weak, and forms high spin complexes.

In an octahedral complex:

• If the fourth d-electron enters the higher-energy $e_g$​ orbitals instead of pairing in $t_{2g}$​, it means that
• the crystal field splitting energy (Δ₀) is small
• pairing energy is larger than Δ₀

This situation occurs when the ligand is weak, leading to high-spin complexes.