I think the option (D) is correct. Here are the reasons.
1. Pairs (x,y) in (A) and (C) do not support the reaction (1) where two isomers give same hyrogenathydr product (Z)
2. Pairs (x,y) in (A),(B),and (C)do not support the formation of same two ozonolysis products (W) and (S) as stated in reaction (2).
3. Pairs (x,y) in D are two geomtrical isomers (trans and cis respectively). They support all the reactions in steps 1 to 3 and the melting point of trans isomer (x) is higher than the cis one(y).
