Question

instead of relying solely on a password to control access to a network, this adds another layer of protection.
two - factor authentication
information theory
symmetric encryption
multiplexing

Explanation:

Two - factor authentication requires an additional verification step beyond just a password, adding an extra layer of protection for network access. Information theory deals with the quantification, storage, and communication of information. Symmetric encryption is about using the same key for encryption and decryption. Multiplexing combines multiple signals into one for transmission.

Answer:

A. Two - factor Authentication