The role of the certificate authority (CA) as a third party is to:

A. provide secured communication and networking services based on certificates.

B. host a repository of certificates with the corresponding public and secret keys issued by that CA.

C. act as a trusted intermediary between two communication partners.

D. confirm the identity of the entity owning a certificate issued by that CA.

Explanation:

The primary activity of a CA is to issue certificates. The primary role of the CA is to check the identity of the entity owning a certificate and to confirm the integrity of any certificate it issued. Providing a communication infrastructure is not a CA activity. The secret keys belonging to the certificates would not be archived at the CA. The CA can contribute to authenticating the communicating partners to each other, but the CA is not involved in the communication stream itself.