A saturated solution of CaF2 is initially at pH 7. Which statement best describes the qualitative effect of raising the pH to 12?
a) The salt becomes more soluble because F− ions are protonated to form HF.
b) The solubility is essentially unchanged because CaF2 is a salt of a strong acid and a strong base.
c) The salt becomes less soluble because fewer F− ions are protonated at high pH.
d) The salt becomes more soluble because Ca2+ ions precipitate as Ca(OH)2, removing Ca2+ from solution.