Which of the following types of authentication is represented by using a four-digit PIN to access a mobile device?

A. multifactor

B. FIM

C. mutual

D. single-factor

Explanation:
Single-factor authentication is represented by using a four-digit personal identification number (PIN) to access a mobile device. Single-factor authentication occurs when a single type of information is required to authenticate a user. There are typically three types of authentication: something you know, something you have, and something you are. A user who supplies a PIN to access a mobile device is using single-factor authentication; the user is supplying only one type of authentication: something the user knows. The PIN is the authentication factor in this scenario. It is important to note that user names are a form of identification, not authentication. Therefore, providing a user name and password is also single-factor authentication. Authentication serves to prove that the identity the user has supplied is correct.

Multifactor authentication occurs when more than one authentication type must be used to authenticate to a system. For example, a user who supplies a user name, password, and six-digit key from a separate physical device is using multifactor authentication: the password is something the user knows, and the device key is something the user has. Other examples of multifactor authentication include passwords used in combination with smart cards or passwords used in combination with an iris scan. Multifactor access solutions like Cisco Duo Security provide the ability to use addition sources of validation, such as phone notifications, Simple Message Service (SMS) messages, or access tokens, to secure access to on-premises as well as cloud-based resources.

Mutual authentication is an authentication system in which hosts offer proof of identity to each other. Kerberos is an example of a mutual authentication system. Kerberos is a single sign-on (SSO) access control system that was developed by Project Athena at the Massachusetts Institute of Technology (MIT). Once a client is authenticated by Kerberos, the client receives a ticket-granting ticket (TGT) and a session key. When the client wants to access a particular network device or service, the client presents the TGT and the session key to a ticket-granting server (TGS). The TGS verifies the identity of the user to other devices or services on the network.

Federated identity management (FIM) is the process of providing access to a company’s data resources to organizations or parties that are not owned by the company. For example, a client who buys Internet advertising from a mass media company might want to access performance reports instead of relying on the company to generate reports. FIM would enable the client to access reporting information directly from the mass media company’s network.

Reference: https://duo.com/blog/two-factor-authentication-the-basics