Final answer:
The position that was not part of an Indian agency's staff is a light horseman.
Step-by-step explanation:
The position that was not part of an Indian agency's staff is D. a light horseman. The Indian agency staff were responsible for various roles in the Indian reservations, including healthcare (such as nurses and doctors), maintenance (like groundskeepers), and community services. However, a light horseman does not fall under the typical roles of an Indian agency's staff.
Learn more about Indian agency staff positions