He could not confirm that he had made any such statement.

Answer: Option C

Confirm : establish the truth or correctness of (something previously believed or suspected to be the case).
Reject : dismiss as inadequate, unacceptable, or faulty.
Avoid : keep away from or stop oneself from doing (something).
Deny : state that one refuses to admit the truth or existence of.
Refuse : indicate or show that one is not willing to do something.

Antonym of Confirm is Deny