The correct option is C a,d
Condition to show geometrical isomerism : XYC=CXY
X and Y must have different groups/atoms attached to carbon on the same side of double bond.
Among given compounds, only pent-2-ene and hex-2-ene can show geometrical isomerism.
Ethene have identical atoms on the same side of double bond; therefore, it cannot show geometrical isomerism.
Butane does not have double bond, thus it will not show geometrical isomerism.
Hence, the correct answer is option (c).