The common ion effect occurs when a solution contains two substances, blank. According to the blank, the presence of blank, shifts an equilibrium of the dissociation towards the _____.
a) Acids; H⁺ ions; acids; neutralization
b) Bases; OH⁻ ions; bases; ionization
c) Ions; a common ion; ions; precipitation
d) Salts; a common ion; salts; precipitation