Answer: Option A
:
A
The compounds with each doubly bonded carbon attached to two different groups (like Cab=Cab, Cab=Ccd) exhibit geometrical isomerism i.e., cis and trans forms. The geometrical isomerism arises due to the restricted rotation of the double bond.
However, even though there is restricted rotation for a triple bond, alkynes do not exhibit geometrical isomerism, since the triply bonded carbons are attached to only one group each.