Transcript text: In the following reaction, what substance gains electrons? $2 \mathrm{Fe}^{3+}(\mathrm{aq})+\mathrm{Sn}^{2+}(\mathrm{aq}) \rightarrow 2 \mathrm{Fe}^{2+}(\mathrm{aq})+\mathrm{Sn}^{4+}(\mathrm{aq})$
(A) $\mathrm{Fe}^{3+}(a q)$
(B) $\mathrm{Sn}^{2+}(a q)$
(C) $\mathrm{Sn}^{4+}(a q)$
(D) $\mathrm{Fe}^{2+}(a q)$
(E) $\mathrm{H}_{2} \mathrm{O}(l)$