An alkene A gives only the compound shown on ozonolysis followed by $\mathrm{Zn}$/$\mathrm{H}{}_2\mathrm{O}$. Which alkene is A?

The compound shown is propanal. Only a symmetrical alkene gives one carbonyl compound, and two molecules of propanal combine back through a double bond to form hex-3-ene. But-2-ene would give ethanal, pent-2-ene gives propanal and ethanal, and but-1-ene gives methanal and propanal.