Final answer:
Certificate-based authentication enables users to use PIV or CAC cards to log in to Now Platform or Service Portal.
Step-by-step explanation:
The correct answer is a. Certificate-based authentication. Certificate-based authentication enables users to use PIV or CAC cards to log in to the Now Platform or Service Portal. These cards contain a digital certificate that is used to verify the user's identity.
When a user logs in with a PIV or CAC card, the system checks the card's certificate against a trusted authority to ensure its authenticity. This provides a higher level of security compared to other authentication methods.