Final answer:
B-roll is the term for video footage that accompanies a TV news story in the background while a reporter speaks over it. It provides visual context and supplements the main content, which is known as A-roll.
Step-by-step explanation:
The alphabetic name for the video footage used to accompany a TV news story as a reporter speaks over it is called B-roll. This refers to the additional footage that is intercut with the main shot, or A-roll, which typically contains the primary audio and video content. The purpose of the B-roll is to add greater depth to the story, provide visual interest,and assist in reinforcing the reporter's narration. Often, B-roll features supplemental images, such as scenes of locations, people, or activities related to the story being told. This kind of footage is essential in television production and filmmaking, where visual storytelling is a key component.