Something the users knows includes EXCEPTa.Identity badgesb.Passphrases and Mothers Maiden namec.A secret handshaked.Passwords and PIN numbers

To determine the correct answer to the question regarding what users know, we can analyze each option:

1. Identity badges: These are physical items typically issued by an organization, not something the user personally knows. Therefore, it's not a "knowledge" factor.

2. Passphrases and Mother's Maiden Name: Both of these are items that a user knows. Passphrases are crafted by the user, and a mother's maiden name is often used for security questions and personal verification.

3. A secret handshake: This is a behavioral gesture or action rather than an item of knowledge in the context of personal identification or security mechanisms. It's also less commonly used in standard security protocols.

4. Passwords and PIN numbers: Both of these are critical pieces of information that a user knows and uses to authenticate their identity in digital spaces.

Final Answer:

The correct answer is a. Identity badges, as this is not something a user knows in the same way as the other options, which are all forms of personal knowledge or securely remembered information.