_________ is not a file extension of a video file.

Correct option is D

The correct answer is (d) pdf.
Explanation:
● .pdf stands for Portable Document Format; it is a document file extension, not a video file extension.
● The other three are common video containers.
Information Booster:
● .mp4 is the most widely compatible video format.
● .mov was developed by Apple.
● .avi was developed by Microsoft.
Additional Knowledge:
● mov – QuickTime Movie format.
● avi – Audio Video Interleave format.
● mp4 – MPEG-4 Part 14 format.