I believe they’re referring to the Tuskegee Airmen. Here a link to an article about them https://www.google.com/amp/s/www.history.com/.amp/topics/world-war-ii/tuskegee-airmen
The main reason why the United States largely shied away from imperialism prior to 1890 was because it was still a relatively "fragile" nation with a host of its own issues to work out--such as the slavery issue that eventually led to the devastating Civil War.
It would be A. Examples of civilizations in the Arabian Peninsula hope his helps
