Consider the cathodic protection of a buried iron pipeline. Given $E^{\circ }(\mathrm{Fe}{}^{2+}/\mathrm{Fe})=-0.44\mathrm{V}$, $E^{\circ }(\mathrm{Zn}{}^{2+}/\mathrm{Zn})=-0.76\mathrm{V}$, $E^{\circ }(\mathrm{Cu}{}^{2+}/\mathrm{Cu})=+0.34\mathrm{V}$. Which statements are correct?

1. AA block of copper connected to the pipeline would act as a sacrificial anode
2. BIn impressed-current protection the pipeline is connected to the negative terminal of a DC source so that it becomes a cathode
3. CA zinc block connected to the pipeline is oxidised in preference to iron because $E^{\circ }(\mathrm{Zn}{}^{2+}/\mathrm{Zn})$ is more negative than $E^{\circ }(\mathrm{Fe}{}^{2+}/\mathrm{Fe})$
4. DOn the protected iron surface in aerated neutral soil water, the main cathodic reaction is $\mathrm{O}{}_2+2\mathrm{H}{}_2\mathrm{O}+4\mathrm{e}{}^{-}\to 4\mathrm{OH}{}^{-}$