# Which of the following compounds will exhibit cis-trans (geometrical ) isomerism ?

$(a)\;2-Butene \\ (b)\;2-Butyne \\ (c)\;2-Butanol \\ (d)\;Butanal$

Cis -trans(geometrical ) isomerism is exhibited by those compounds which have same structural formula but different spatial arrangement of groups around $C \equiv$ (carbon- carbon) double bond.
Hence a is the correct answer.