Two-factor authentication (2FA) is a security process that requires users to provide two different authentication factors to verify their identity. This means that in addition to providing something they know (such as a password or PIN), they must also provide something they have (such as a smart card or token) or something they are (such as a fingerprint or retinal scan).
In this case, the correct answer would be C. Password/thumbprint. This option meets the requirement for two-factor authentication because it combines two different types of authentication factors: something the user knows (the password) and something the user is (the thumbprint). The other options do not meet the requirement for 2FA because they either use only one type of authentication factor (A and D) or use two instances of the same type of factor (B).