The correct option is B Trans-hex-3-ene
Cis isomer of acyclic system is less stable than trans isomer. This is due to the steric hindrance between the terminal groups is always greater in Cis isomer than trans isomer.
Trans isomers are more stable than cis isomer. In trans isomers same group of atom on two different carbon atoms are located on the opposite sides of the carbon double bond and thus lesser steric hinderance is present in trans molecule. Hence, trans-hex-3-ene isomer is stable than cis-hex-3-ene isomer.