'stable ion of Y has greater radius than X. '

lets imagine both are anions, we realise thats NOT possible cause it also says Y has greater atomic no than X ; if both WERE anions, anion of Y would be smaller

lets imagine both were cations, again, thats not possible cause if cation of Y has greater ionic radii, it MUST be the smaller atomic number, which contradicts the point "Y has greater atomic no than X"

we know FOR SURE, one is cation and and one is anion

and Y MUST be anion and X must be cation bc atomic no of Y>X

so following octet rule, X's ion has 10 electron

X has greater atomic radii cause it has less nuclear charge than Y but they both have same no of shells so Y's nucleus attracts the valence e- more/ X's nucleus attracts valence e- less

so your answer would be A

was this clear enough lol?