I think its either b or a mostly a though hope this helps!!
A plot is closely related to subject matter. This is where the story that is written directly discusses the general theme or the general subject that will be portrayed by the writer through his thorough writing. Plots are designed for readers to understand the material's overall content and how the story would probably go.
Maybe it could be about the benefits and challenges?
A. true. I actually attended that opera in 2012!
Almost, change illustrating with to illustrate. But otherwise it looks right to me.
