Answer:
its copyright has expired
Explanation:
If a work is in the public domain it means that it's copyrighte has been expired.
After the period of copyright protection has expired, a work becomes available for use without permission from the copyright owner; it is now said to be "in the public domain." Most works enter the public domain because their copyrights have expired.
Answer:
Wikipedia
Explanation:
Most people go to other websites because they don't like to read the articles, they just want the information now, but Wikipedia has some of the most detailed articles on information to do with anything, and it's free to use.
Answer: keeps confidential documents secure,
displays a GUI, allocates the computer's resources, and retrieves files
Explanation:
The operating system can be defined as the software installed in the system that provides the information and services to the users by controlling the hardware, software resources, and regulates the computer programs. It runs the applications and programs in the system, displays the graphic user interface for the services, stores, manipulates, and retrieves files. It prevents the unauthorized access to the data and programs by using passwords thus provides the security to the system and documents.