Answer:
a. decrease the amount of the common ion in the system
Step-by-step explanation:
The correct option is - a. decrease the amount of the common ion in the system
Reason -
Adding a common ion decreases solubility, as the reaction shifts toward the left to relieve the stress of the excess product.
Adding a common ion to a dissociation reaction causes the equilibrium to shift left, toward the reactants, causing precipitation.