Which statement about file extensions is true?

• A. They identify the owner of the file
• B. They indicate the file size
• C. They determine the file creation date
• D. They indicate the program used to open the file

Answer: (D)

File extensions are labels that tell the operating system what type of content a file holds and which program should be used to open it. The part after the final dot—like .txt, .docx, or .jpg—serves as a hint about the format, so double-clicking a file or choosing open will launch the appropriate application that can read that content. This is why the statement is true: the extension directly guides which program handles the file.

Ownership, size, and creation date are different kinds of information stored by the filesystem or the file's metadata, not determined by the extension. For example, a .txt file can be opened by a text editor, a .jpg by an image viewer, and these associations help the system pick the right tool, independent of who owns the file or how large it is. If a file is mislabeled with an incorrect extension, the system may not recognize the type correctly, which underscores that the extension’s role is about choosing the program, not about ownership, size, or creation time.