What Is Single-Factor Authentication

What is single-factor authentication?

A) The traditional security process that requires a user name and password.
B) A process that requires the user to provide two means of authentication, what the user knows (password) and what the user has (security token) .
C) A process that requires more than two means of authentication such as what the user knows (password) , what the user has (security token) , and what the user is (biometric verification) .
D) The identification of a user based on a physical characteristic such as a fingerprint, iris, face, voice or handwriting.