Windows identifies which application to open a file with by examining which of the following?

• A. The file extension
• B. The file signature at the beginning of the file
• C. The file attributes
• D. The file signature at the end of the file

Answer: (A)

Windows uses the file extension to decide which program should open a file by default. The extension, the suffix after the last dot (like .txt, .docx, or .jpg), maps to a specific application in the system registry. When you open a file, Windows looks up that extension, finds the associated program, and launches it with the file as an argument. You can change this association if you want a different program to open that type of file.

File signatures at the beginning or end of a file are about identifying the file’s type from its content, not about which application Windows uses by default. File attributes are metadata about the file (like read-only or hidden) and do not determine the opening program.