Which set of actions satisfy the requirement for multifactor authentication? 

Answer options:

A. The user enters a user name and password, and then re-enters the credentials on a second screen.
B. The user swipes a key fob, then clicks through an email link.
C. The user enters a user name and password, and then clicks a notification in an authentication app on a mobile device.
D. The user enters a PIN into an RSA token, and then enters the displayed RSA key on a login screen.

C

This is an example of how two-factor authentication (2FA) works: 1. The user logs in to the website or service with their username and password. 2. The password is validated by an authentication server and, if correct, the user becomes eligible for the second factor. 3. The authentication server sends a unique code to the user`s second-factor method (such as a smartphone app). 4. The user confirms their identity by providing the additional authentication for their second-factor method.