Kerberos provides an integrity check service for messages between two
entities through the use of:

A.
A trusted, third-party authentication server

B.
A checksum

C.
Credentials

D.
Tickets

Explanation:
Achecksum that is derived from a Kerberos message is used to verify
the integrity of the message. This checksum may be a message digest
resulting from the application of a hash function to the message. At the
receiving end of the transmission, the receiving party can calculate the
message digest of the received message using the identical hash algorithm
as the sender. Then the message digest calculated by the receiver
can be compared with the message digest appended to the message by
the sender. If the two message digests match, the message has not been
modified en route, and its integrity has been preserved.
For answers Credentials and Tickets are authenticators used in the process of
granting user access to services on the network. Answer “A trusted, third-party authentication
server” is the AS or
authentication server that conducts the ticket-granting process.