What file extension represents a Flash ActionScript source code file?

The correct choice is .as file, which is the file extension specifically associated with ActionScript source code files. ActionScript is the scripting language used in Adobe Flash and Adobe Animate to create interactive content. These files contain the code that defines the behavior of objects in a Flash application or animation, allowing developers to manipulate graphics, control animations, and handle user interactions programmatically.

The other file extensions relate to different types of content used within the Adobe Flash and Animate ecosystem. The .swf file extension represents a compiled Flash file that contains the final output of the animation or application, which can be played back in a Flash Player or web browser. The .flv file extension is associated with Flash Video files, used for storing video content for playback. The .xml file extension denotes XML files, which are structured text files often used for data storage and transfer but not specifically for ActionScript code.

In summary, the .as file extension is uniquely designated for ActionScript source code, making it the correct choice for this question.