Answer:
Many cities were overcrowded with limited housing and few sanitation services.
Explanation:
During the late 1800s, urban areas grew very fast because economic opportunities were better than in the countryside. This attracted people from rural areas, and also from abroad, who flocked to the cities too fast for the cities infraestructure to keep up with.
This made most cities at the time very overcrowded, with few public services that were overstrained, and with serious problems in terms of sanitation and public safety. However, people could still earn higher incomes than in the countryside, and despite all these problems, the cities did not stop being attractive for both domestic and international migration.
Answer:
D) The transfer of peoples, diseases, plants, and animals between the new old worlds.
