In the oxidation-reduction reaction
$\ce{Sn^{4+} + 2 Fe^{2+} -> 2 Fe^{3+} + Sn^{2+}}$
(A) $\ce{Sn^{4+}}$ is the oxidizing agent and $\ce{Fe^{2+}}$ is the reducing agent.
(B) $\ce{Sn^{4+}}$ is the reducing agent and $\ce{Fe^{2+}}$ is the oxidizing agent.
(C) $\ce{Sn^{4+}}$ is the reducing agent and $\ce{Fe^{3+}}$ is the oxidizing agent.
(D) $\ce{Fe^{3+}}$ is the oxidizing agent and $\ce{Sn^{2+}}$ is the reducing agent.
My thoughts: Because $\ce{Sn^{4+}}$ is getting reduced, and $\ce{Fe^{2+}}$ is getting oxidized, then $\ce{Sn^{4+}}$ is therefore an oxidizing agent, and $\ce{Fe^{2+}}$ is a reducing agent, which leads me to believe that A is the right answer. However, the answer key says D. I note that (D) is true for the reverse reaction, but why would A not be true then?
