Answer:
for this one, your answer will be B.X
Explanation:
It is X because each element in x is mapped to exactly one element in y.
In X 6 maps to 4,2; in y 6 maps to 6,2; in Z 7 maps to 2,8.
so every element in x should map to exactly one element in y and it is possible only in the set X so the answer is X.
hope it helps....
have a great day.