Final answer:
The correct answer is b) Certificate authority, which is responsible for real-time lookups and validation of digital certificates via CRLs or OCSP.
Step-by-step explanation:
Elton needs a real-time lookup of a digital certificate's status to ensure it is valid and has not been revoked. The correct answer is b) Certificate authority. A Certificate authority (CA) is responsible for issuing and managing security certificates and public keys that are used in cryptography. One of the services a CA provides is the distribution of Certificate Revocation Lists (CRLs) or the use of the Online Certificate Status Protocol (OCSP) which allows for real-time validation of certificates. Cybersecurity relies on such protocols to maintain the integrity and security of online communications.