I would have to say it's part of the theme.
Morality and politics is the ethos of the story, aka origin aka theme.
With-out a theme there would be no plot...and no setting.
So...
C. Theme
Assuming you meant a yacht, the answer would be B. a large boat.
The answer is a sorry if it's wrong....
I am not perfect at this but I think it would be C. A is comparing the price of a cruise to the price of an island, B - the either and maybe do not flow together, and in D groomed and fed are in past tense and water and clean are present.
