(20 14? At a certain temperature, the precipitation and dissolution equilibrium curves of three kinds of carbonate mco3 (m2+:Mg2+, Ca2+, Mn2+) are shown in the following figure.

A. When A.pM is equal, the larger the value of p(CO32-) in the figure, the smaller the actual concentration. Therefore, the Ksp of MgCO3, CaCO3 and MnCO3 decreases in turn, so A is wrong;

B. According to A, the Ksp of MgCO3, CaCO3 and MnCO3 decreases in turn, so in 100 ml saturated mixed solution of MgCO3, CaCO3 and MnCO3, the concentration of Mn2+ is the smallest, so if K2CO3 solution with sufficient concentration is added, the quality of MnCO3 precipitated is the least, so B is wrong;

Point C. B can represent the saturated solution of CaCO3, and PM < P (CO32-), so C (Ca2+) > C (CO32-), so C is wrong;

D. The greater the PM value, the smaller the actual concentration, and point C can represent the unsaturated solution of MgCO3; If CaCO3 is a supersaturated solution, CaCO3 will precipitate, so d is correct;

Therefore, choose: d.