in the context of "authentication ",which of the following is correct description of a user's "identity" or "identifier"?
1. Typically, it is the alphanumeric user id used to an application/system. It uniquely identifier the user
2. it is the user's biometric identifier such as thumb impression. it uniquely identify the user
3. it is the electronic identifier assigned to the user to uniquely identify him/her E.q. The RFID enabled ID card
4. All of the above
