Theme is established through the conflicts and their resolution. Theme is conveyed as a message about a topic related to the plot.
These two options are the best choices. A theme is the author's main idea or message that is created through the text. it often is connected to the plot because the struggles of the characters are often how the message is conveyed. For example, the movie Finding Nemo has themes about allowing your children to have some independence and also believing in yourself. Marlin has to learn to trust that Nemo can do things on his own and it's okay for him to explore. Nemo also has to learn to believe in himself, but also listen to his father in some situations.