The correct answer is: A. Music
A medium can be defined as a method of transmission. A medium can transmit or convey: messages, ideas, opinions etc. The plural of medium is "media", and as we know, different types of media include: movies, television series, news, print media, etc. Music is considered a medium, since it is a tool through which information is conveyed to listeners, in the form of: vocals, beats, instrumental sounds, lyrics, etc.