Get insightful responses to your questions quickly and easily on IDNLearn.com. Discover prompt and accurate answers from our experts, ensuring you get the information you need quickly.

Which of the following is a common reason for an "authentication unsuccessful" error?
A) The user has not set up a password yet.
B) The network connection is disconnected.
C) The username or password entered is incorrect.
D) The device’s screen brightness is too low.