Among the three options KCl,NaCl and MgCl2, the size of anion is same. So, larger the cation, larger will be the cation/anion ratio i.e., KCl will have larger cation/anion ratio among the three. So, we left with two options KCl and CaF2. Among these two CaF2 will have maximum value of cation/anion ratio because decrease in ionic radii of anion from Cl−to F−does not overcome the effect of decrease in ionic radii of cation from K+to Ca2+.