A Swimming Pool Was Sufficiently Alkaline So That the Carbon

Multiple Choice

A swimming pool was sufficiently alkaline so that the carbon dioxide absorbed from the air produced a solution in the pool that was 2 × 10^-4 M in carbonate ion.If the pool originally contained 4 × 10^-3 M Mg²⁺,6 × 10^-4 M Ca²⁺,and 8 × 10^-7 M Fe²⁺,then the precipitate that was formed consisted of ________.
(K_sp values are: CaCO₃,4.7 × 10^-9;MgCO₃,4.0 × 10^-5;FeCO₃,2.0 × 10^-11)

A) only MgCO₃
B) only CaCO₃
C) only FeCO₃
D) only CaCO₃ and FeCO₃
E) MgCO₃,CaCO₃,and FeCO₃