Many immigrants in the 1800’s arrived by boat at Ellis Island. Which passengers were required to have medical inspections and cross examinations by Ellis Island agents before they were allowed into the country?

D.  third-class and steerage-class passengers

Explanation:

Once the immigrants reached Ellis Island, the first and second class passengers were allowed to get off at New York harbour. The third class and steerage-class passengers however, would be sent to Ellis island.

On Ellis island, the passengers would go through medical examinations and cross examination to determine if they were fit enough to enter the US. The logic was that people in third and steerage classes were more likely to be diseased as they were poorer.

the effect of the ming leaders banning ships with more than two masts was that there was no further construction of ships masts, because there was a surplus. ming emperors disallowed foreign exploration