The correct answer is A: Unimportant.
An example of an extra in a movie is when the main characters are walking down the street in Manhattan and there are a bunch of people walking in the background. The people that are walking in the background are the extras because they are unimportant for the scene. Extras are there so when you watch a show, movie, broadway, e.t.c, it won't look like the performance is empty. Just think of how the main characters would be walking down the street with an empty road around them. How much more boring than having extras in the background would that be?
I hope this helped! Stay cool! :-)
