I believe the correct answer would be A
The correct answer is plot. Theme is the work's main idea (the "why" of the work), and there usually are more themes in a single work. Narrator is the "I" of the story, someone who tells it. The setting is the "when and where" of the story, the time-place frame. The plot is the "what" - what happens.
The relationship between Prospero and Caliban-correct on apex
These words have similar meanings, so the relationship between them is that they are "synonyms". Synonyms are words with similar meanings, and they can often be used interchangeably within a sentence. Other relationships could include antonyms, which are words with opposite meanings.