The alkene shown gives a single carbonyl compound on ozonolysis with reductive work-up. Which of the alkenes in the options also give only a single carbonyl compound (count compounds, not molecules)?

The compound shown is but-2-ene, which gives only ethanal. A single compound results when the alkene is symmetrical, or when it is a ring (giving one dialdehyde). 2,3-Dimethylbut-2-ene gives only propanone and cyclohexene gives only hexanedial. Pent-2-ene gives propanal and ethanal, and 2-methylpropene gives propanone and methanal.