Which of the following is an example of multifactor authentication?

Multifactor authentication (MFA) enhances security by requiring users to provide two or more verification factors to gain access to a resource, such as an online account or application. This method aims to increase the certainty that the user is indeed who they claim to be.

In the context of the correct answer, when a user inputs both a password and a verification code sent to their phone, they are demonstrating multifactor authentication. The password represents something the user knows, while the verification code sent to the phone represents something the user possesses. This combination makes it significantly more difficult for unauthorized users to access the account, even if they know the password, as they would also need access to the user’s phone to retrieve the verification code.

The other options lack the multifactor aspect. Using the same password across multiple sites does not provide any additional security, as it relies solely on one factor: the password itself. Answering a security question typically involves knowledge-based authentication, which also counts as just one factor since it doesn't require a second method of verification. Similarly, providing an email for account recovery is a single point of access and does not incorporate any additional factors for authentication. Therefore, option B correctly exemplifies multifactor authentication, strengthening the security measures in place for