The definition that best describes piracy as it relates to the music business is (a) Unauthorized copying and distribution of music
Piracy in the music business refers to the act of making copies of music or distributing it without permission from the artists or those who own the rights to the music. Imagine you have a favorite musician or band, and they worked hard to create their songs.
Piracy would be like someone making copies of those songs without paying for them or getting permission, and then sharing those copies with others. This is not allowed because it takes away the opportunity for the artists to earn money for their work.
So the correct option would be A.