Answer:
d. If X is NP - complete and Y is in NP then Y is NP - complete.
This can be inferred
Step-by-step explanation:
The statement d can be inferred, rest of the statements cannot be inferred. The X is in NP complete and it reduces to Y. Y is in NP and then it is NP complete. The Y is not in NP complete as it cannot reduce to X. The statement d is inferred.