In the Wacker process $\mathrm{PdCl}{}_2$ and $\mathrm{CuCl}{}_2$ catalyse the oxidation of ethene by $\mathrm{O}{}_2$ in water. The steps are $\mathrm{C}{}_2\mathrm{H}{}_4+\mathrm{PdCl}{}_2+\mathrm{H}{}_2\mathrm{O}\to \mathrm{CH}{}_3\mathrm{CHO}+\mathrm{Pd}+2\mathrm{HCl}$, $\mathrm{Pd}+2\mathrm{CuCl}{}_2\to \mathrm{PdCl}{}_2+2\mathrm{CuCl}$ and $2\mathrm{CuCl}+\frac{1}{2}\mathrm{O}{}_2+2\mathrm{HCl}\to 2\mathrm{CuCl}{}_2+\mathrm{H}{}_2\mathrm{O}$. For $5.6\mathrm{L}$ of ethene at STP converted completely (C = 12, H = 1, O = 16), which option is correct?

1. A$5.5\mathrm{g}$ of $\mathrm{CH}{}_3\mathrm{CHO}$; $\mathrm{O}{}_2$ oxidises Pd(0) directly and Cu is not needed
2. B$11.0\mathrm{g}$ of $\mathrm{CH}{}_3\mathrm{CHO}$; Pd stays in the +2 state throughout and Cu is the only species that changes
3. C$11.0\mathrm{g}$ of $\mathrm{CH}{}_3\mathrm{CHO}$; Pd cycles between +2 and 0 and $\mathrm{O}{}_2$ is the terminal oxidant
4. D$22.0\mathrm{g}$ of $\mathrm{CH}{}_3\mathrm{CHO}$; Pd cycles between +2 and 0 and $\mathrm{O}{}_2$ is the terminal oxidant