Which of the following is NOT a video file extension commonly used for storing digital video?

Introduction / Context:
Different types of multimedia content use different file formats and extensions. Video files, audio files, and images each have their own typical extensions. For basic computer literacy and for working with media software, you should be able to recognise which extensions belong to video formats and which do not. This question asks you to identify which extension in the list is not used for video files.

Given Data / Assumptions:

• The file extensions listed are .flv, .mov, .mp3, and None of the above.
• Video files contain moving images and often sound, stored in formats such as .mp4, .avi, .mov, .flv, etc.
• Audio only formats use extensions such as .mp3, .wav, and .aac.
• We assume common consumer multimedia formats.

Concept / Approach:
The .flv extension stands for Flash Video, a format that was widely used on streaming sites in the past. The .mov extension is associated with Apple QuickTime and is used for video files. In contrast, .mp3 is primarily an audio format used to store compressed music and sound recordings; it does not store video frames. When a question asks which is not a video file extension, we must pick the extension used for audio only. Therefore, .mp3 is the correct answer, as it is an audio format, not a video file format.

Step-by-Step Solution:
Step 1: Identify .flv. .flv is Flash Video, used for streaming video content on the web. Step 2: Identify .mov. .mov is a QuickTime video format from Apple and stores video along with audio. Step 3: Identify .mp3. .mp3 is a widely used audio format that compresses sound, especially for music files, and does not include video frames. Step 4: Match these with the question requirement. The question asks for a file extension that is not for video, so .mp3 fits this description. Step 5: Recognise that “None of the above” cannot be correct because we have already found a non video extension.

Verification / Alternative check:
Multimedia software such as media players, video editors, and conversion tools list supported formats. They classify .mp3 under audio formats, while video lists include formats like .mp4, .avi, .mov, .mkv, .flv, and others. Documentation for .mp3 describes it as MPEG Audio Layer 3, clearly emphasising audio compression. Meanwhile, .mov and .flv are described as video container formats that may also contain audio tracks. This confirms that .mp3 is not a video file extension, while the other listed extensions are tied to video.

Why Other Options Are Wrong:
Option A (.flv): This is a video file format associated with Adobe Flash and used for streaming video. Option B (.mov): This is a QuickTime movie format and is used to store video content. Option D (None of the above): Incorrect because .mp3 is clearly an audio only format and not a video file extension.

Common Pitfalls:
Some learners may see that .mp3 often appears in playlists and media folders and assume that any media extension must be video related. Others might not recognise .flv because it is older, but they should still realise that .mp3 is identified with music files rather than movies. To avoid confusion, remember that video files usually have extensions like .mp4, .avi, .mov, .flv, and .mkv, while .mp3 is strongly associated with compressed audio only.

Final Answer:
The extension that is not a video file type is .mp3, which is an audio format, not a video format.