Final answer:
The theme best supported by the setting in this passage from My Antonia is that life is very difficult for immigrants.
Step-by-step explanation:
The theme best supported by the setting in this passage from My Antonia is A. Life is very difficult for immigrants. The description of the rough red hillocks, the broken-down shed and windmill, and the door and window sunk in the drawbank all paint a picture of a challenging and harsh environment. This setting reflects the struggles faced by the Shimerdas, who are immigrants trying to make a living on the prairie.