The bromide shown is heated with $\mathrm{AgCN}$ and the product is reduced with $\mathrm{H}{}_2$ over Ni. Which structure is the final product?

AgCN gives the isocyanide, ethyl isocyanide (N-bonded). Catalytic hydrogenation reduces the isocyanide carbon to a methyl group on nitrogen: $\mathrm{R}-\mathrm{N}\equiv \mathrm{C}\to \mathrm{R}-\mathrm{NH}-\mathrm{CH}{}_3$, giving N-methylethanamine (a secondary amine). Propylamine would be the reduced KCN nitrile, and the other amines have the wrong carbon skeleton.