Apple Certified Support Professional Practice Test

The appearance of a question mark next to the login prompt on a Mac's login screen typically indicates that the computer is unable to locate the startup disk. This situation arises when the system cannot find a valid bootable volume, which may occur due to various reasons such as a disconnected or corrupted disk, a missing operating system, or hard drive failure. Consequently, the system does not have the necessary files and settings to complete the login process, and this warning icon serves to alert the user that attention is needed.

In contrast, other scenarios presented in the options, while they may relate to different issues, do not specifically correlate with the question mark indication at the login screen. For instance, an incorrectly configured account would generally present a different error message or prompt for further action. Similarly, if a password has been forgotten, the user would typically receive a prompt to re-enter their credentials without any indication of missing hardware. Lastly, while the system starting up does show a loading indicator or progress bar, it would not show a question mark if the login screen is already present. Thus, the question mark specifically signifies the inability to find the startup disk.