The major product P of the given reaction is · ABC26OR0554

KH gives the potassium alkoxide, which undergoes an anionic oxy-Cope [3,3] shift. The vinyl C=C and the ring C=C of the bicyclo[2.2.2]octene form the 1,5-diene. The C(O⁻)–bridgehead σ-bond breaks and a new C–C bond forms between the vinyl terminus and the ring alkene carbon. This opens the bicycle into a fused 6/6 system: a cyclohexene ring plus a ring that carries the enolate, which becomes the ketone on work-up. The rigid bicyclic frame forces a boat-like transition state, so the two ring-fusion H atoms end up on the same face, giving a cis-fused octalone. In (d) the ketone sits β to the non-allylic ring-fusion carbon and both junction H are hashed (cis). Answer (d).