Which statement about file extensions is accurate?

• A. They identify the file type to the system
• B. They encrypt the file name
• C. They determine the user’s permissions
• D. They are optional and always hidden

Answer: (A)

File extensions identify the file type to the system. The part after the dot in a filename (like .txt, .jpg, or .pdf) tells the operating system what kind of data the file holds and which program should open or handle it. That association lets the OS pick the right application, apply appropriate icons, and interpret the contents correctly. They aren’t about encrypting the file name or controlling who can access the file, and while some systems can hide extensions, they aren’t inherently optional or always hidden—the extension still serves as a cue for how to work with the file.