A confidential number used as an authentication factor to verify a user's identity is called a:

a, PIN

b. User ID

c. Password

d. Challenge

Answer: (A) PIN

Explanation:

PIN is the personal identification number which is basically used to verify the identity of the users. It is confidential number which is used as the authenticating factor.

The PIN is the combination of the number that is also use to authenticate the banking system with the users.

On the other hand, the other given options are incorrect because these are not used to identify the users identification process.

Therefore, Option (A) is correct.