The most accurate answer is:
... the service company that moves a media file from the producer who makes the media file to multiple online retailers (e-tailers) who sell or stream the media file to customers.
Distributors generally focus on getting media content from producers to various platforms where it can be sold or streamed. While the other options touch on aspects of distribution (e.g., sales, logistics, inventory), they don't capture the primary role of a distributor in the context of media content as clearly as the second option does.