Which of the following is the most important consideration when opening a file on an...

The most important consideration when opening a file on an Operating System Graphical User Interface (OS GUI) is the file extension. A file extension identifies the type of file and determines which software application can open it. In the official CompTIA ITF+ Student Guide, it is stated that:

“The last part of the file name represents an extension, which describes what type of file it is and is used by Windows to associate the file with an application.”

“Files are usually opened by double-clicking them. You may want to open a file in a software product other than the default, however. When you right-click a file, the shortcut menu displays a list of suitable choices, or you can choose Open With and browse for a different application. You can also use the Default Programs applet to configure file associations.”

“Do not change a file's extension if it is shown. If you delete or change the extension, the file will not be associated with the correct program for opening it.”

This means the OS uses the file extension to decide which application to use to open a file. Changing or deleting the extension can result in the file not opening properly because it no longer matches the program expected to open it.