Which statement about file extensions is true?

• A. Extensions are always visible
• B. Extensions indicate the file type and help the OS determine which program opens it
• C. Extensions are encrypted with the file content
• D. Extensions determine the user permissions

Answer: (B)

File extensions are the labels after the last dot in a file name that indicate what kind of data the file contains and guide the operating system in selecting the program to open it. That’s why this statement is true: the extension helps the OS know which application should handle the file, for example, a .txt file opens with a text editor, a .jpg file opens with an image viewer. Extensions aren’t about encrypting the file content, and they don’t determine user permissions. Also, extensions aren’t always visible—some systems hide them by default, and extensions can be misleading if a file is renamed.