I am facing trouble in the following question
In my view cis is less stable than trans. So if prior groups are on the same side of the double bond then it must have less stability. Also conjugated double bond in short non aromatic cyclic system is highly unstable. So 1,2,3,4,5,6,7,8-octahydrobiphenylene (X) should be the least stable. However I could not guess the correct order.