[" In which of the following cells will the emf be independent of "],[" the activity of the chloride ions? "],[" (a) "Zn|ZnCl_(2)(aq,)|Pr(Cl_(2))],[" (b) "Zn|ZnCl_(2)(aq,)|KCl(aq)|AgCl(s),Ag(s)],[" (c) "Ag,AgCl(s)|KCl(aq)|Pr(Cl_(2))],[" (d) "Hg,Hg_(2)Cl_(2)(s)|KCl(aq)|AgNO_(3)(aq_(1))|Ag(s)]