What defines the application that is executed when a data file is opened?

The option that defines the application executed when a data file is opened is the concept of file association. File association refers to the relationship established between a file format and the application that is designated to handle and open files of that format. When a file is opened, the operating system looks at the file's extension, checks its known associations, and then launches the appropriate software that can interpret and display the content of the file.

For instance, if a user attempts to open a document with a ".docx" extension, the operating system will recognize that this file type is associated with a word processing application such as Microsoft Word. Consequently, that application will launch to allow the user to interact with the document properly.

File format, while related, refers specifically to the structure and encoding of the files themselves, such as whether they are text files, images, or spreadsheets. File linkage and file type, although they sound similar to file association, do not encompass the full scope of how operating systems manage these associations for executing applications.

Therefore, the correct understanding hinges on recognizing that file association directly governs which application opens a file based on its type, effectively managing user experience and software utilization efficiently.