Explanation: Non-repudiation is a mechanism which proves that the sender really sent a message. It provides an evidence of the identity of the senderand message integrity. It also prevents a person from denying the submission or delivery of the message and the integrity of its contents. Answer: C is incorrect. Authentication is a process of verifying the identity of a person or network host. Answer: A is incorrect. Confidentiality ensures that no one can read a message except the intended receiver. Answer: D is incorrect. Integrity assures the receiver that the received message has not been altered in any way from the original.