Nonrepudiation can BEST be assured by using:

A.
delivery path tracing.

B.
reverse lookup translation.

C.
out-of-hand channels.

D.
digital signatures.

Explanation:

Internet Protocol (IP) addresses to usernames. Delivery path tracing shows the route taken but does not confirm the identity of the sender. Out-of-band channels are useful when, for confidentiality, it is necessary to break a message into two parts that are sent by different means.