Explanation/Reference:
Explanation:
Two-factor authentication includes two of the following three factors:
Something you know - Password

Something you have - Token

Something you are - Biometrics

A password is something you know, and cannot be used together for two-factor authentication.
Incorrect Answers:
A, B, C: This answer satisfies the requirements for two-factor authentication.
References:
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, p. 163

Systems accountability depends on the ability to ensure that senders cannot deny sending information and that receivers cannot deny receiving it. Because the mechanisms implemented in nonrepudiation prevent the ability to successfully repudiate an action, it can be considered as a preventive control. Source: STONEBURNER, Gary, NIST Special Publication 800-33: Underlying Technical Models for Information Technology Security, National Institute of Standards and Technology, December 2001, page 7

When we encrypt text it is unreadable and referred to as Cipher Text.
The following answers are incorrect:
Encryption: Changing plain text to cipher text is the process of encryption but it isn't the right answer here. Sorry.
Unplain text: Sorry, that's not even a real word. Lol.
Digitally Signed: This answer is related to cryptography but isn't the right answer. We sign items so that the recipient can assure that the document came from the stated individual and it was not modified. A Digital Signature provides Authenticity and Integrity.
The following reference(s) was used to create this question:
Gregg, Michael; Haines, Billy (2012-02-16). CASP: CompTIA Advanced Security
Practitioner Study Guide Authorized Courseware: Exam CAS-001 (p. 4). Wiley. Kindle
Edition.