Which of the following best describes the common-ion effect?
a) The increase in the solubility of an ionic compound when the solution already contains one of the compound’s constituent ions
b) The suppression of a reaction’s rate when a product ion is added to the reaction mixture
c) The reduction in the solubility of an ionic compound when the solution already contains one of the compound’s constituent ions
d) The lowering of an ionic compound’s solubility when any electrolyte, regardless of its ions, is added to the solution