The correct option is B Increases the dissociation of PCl5
For the reaction,
PCl5(g)⇌PCl3(g)+Cl2(g) the addition of inert gases at constant pressure increases the dissociation of PCl5. When an inert gas is added to a system in equilibrium at a constant pressure, then the total volume will increase. Hence, the number of moles per unit volume of various reactants and products will decrease. Hence, the equilibrium will shift towards the direction in which there is an increase in the number of gaseous moles.
In the above reaction, the equilibrium will shift towards the forward direction (shift to the right) because the number of moles of products is more than the number of moles of the reactants.