The pair of compounds that can exist together is:

Two compounds can exist together if they do not react with each other (i.e., no redox reaction).${\text{Fe}}^{3+}$ is an oxidizing agent and ${\text{Sn}}^{2+}$ is a reducing agent. They react.${\text{Hg}}^{2+}$ is an oxidizing agent and ${\text{Sn}}^{2+}$ is a reducing agent. They react.${\text{Fe}}^{3+}$ reacts with ${\text{I}}^{-}$.${\text{FeCl}}_2$ and ${\text{SnCl}}_2$: Both are reducing agents in their lower oxidation states. They do not react with each other and can exist together.