Of the following statements regarding dissociative substitution in an octahedral transition metal complex,

(a) High steric hindrance between ligands in the metal complex favors fast dissociation of ligand.

(b) Increased charge on the metal atom/ion of the complex favours the acceptance of electron pair of the entering ligands.

(c) A pentacoordinated intermediate is observed.

(d) Nature of the entering ligand significantly influences the reaction.

Which are correct?

Correct option is B

In the dissociative mechanism, there is a step in which an intermediate of reduced coordination number is formed that is the M-X bond is fully broken before the M-Y bond begins to form.

where L is an inert ligand, X is labile (leaving ligand) and Y is the entering ligand.

The rate determining step is the slowest elementary reaction. The rate of overall substitution reaction depends only on the concentration of the original complex, [ML₅X] and is independent of the concentration of the incoming ligand Y.

This reaction is of first order in 

gets dissociated is rate determining step. 

A sterically crowded system is unstable and thus breaking/ dissociation of ligand is easy. Hence, high steric hindrance between ligands in the metal complex favors fast dissociation of ligand.
Increase in positive charge on metal leads to increase in interaction between metal and ligand. This increases the M-L bond strength and dissociation is not favored. Hence, increased charge on the metal atom/ion of the complex favors the acceptance of electron pair of the entering ligands.
Ligand dissociation is the rate-determining step, the entering group should have no or very minor effect on the reaction rate.