What is principal authentication?

B$)$ An entity that can be authenticated by a system by using the identifier associated with that entity.

B$)$ and C$)$

C$)$ A person, computer, printer, device, or a group of these. For example, a person can be given a user ID as an identifier, which can then be used by a system to authenticate the user.

All the above options

A$)$ An authentication mechanism in which a user enters a principal value during authentication.