Final answer:
Hexene, being an open-chain alkene, can accommodate a trans C=C double bond, whereas small ring cyclic alkenes like cyclobutene and cyclopropene cannot due to ring strain. Therefore, the correct option is A, D.
Step-by-step explanation:
The question asks which of the following could accommodate a trans C=C double bond. Among the given options, a trans C=C double bond can be present in open-chain alkenes but not in small cyclic alkenes due to the rigidity and angle strain that would be introduced by trying to force a trans configuration in a small ring system.
Option (a) hexene is an open-chain alkene, so it can accommodate a trans double bond. Option (b) cyclobutene, option (c) cyclopropene, and option (d) cyclopentene are all cyclic compounds and the small ring sizes of cyclopropene and cyclobutene would not allow for a trans configuration due to excessive ring strain. However, cyclopentene and larger cyclic systems may in some cases accommodate a trans double bond depending on substitution pattern and ring strain, but without more information, hexene is the most likely to have a trans configuration in the C=C double bond.