Answer:
The service of African-Americans in the military had dramatic implications for African-Americans. Black soldiers faced systemic racial discrimination in the army and endured virulent hostility upon returning to their homes at the end of the war.
The correct answer is option C: someone diagnosed with smallpox.
The person that would have been most grateful for the work of 19th-century scientist Edward Jenner, would be someone diagnosed with smallpox because Jenner was who discovered the first vaccine against the smallpox virus. Moreover, this disease that was widely spread in the 18th century and killed many people.
