Which of the following compounds is most likely to undergo base-induced elimination by the E1cB mechanism with $\mathrm{NaOEt}$ in ethanol?

E1cB needs a beta-hydrogen made acidic by an electron-withdrawing group and a leaving group, even a poor one, on the next carbon. $\mathrm{CH}{}_3\mathrm{COCH}{}_2\mathrm{CH}{}_2\mathrm{OCH}{}_3$ has hydrogens alpha to C=O (pKa about 20) and a methoxy group on the beta-carbon. The others have no acidifying group; alkyl halides eliminate by E2 or E1.