The answer is c :)
hope this helps
Answer:
The Columbian exchange, also known as the Columbian interchange, named after Christopher Columbus, was the widespread transfer of plants, animals, culture, human populations, technology, diseases, and ideas between the Americas, the Old World, and West Africa in the 15th and 16th centuries.
D. Crowded, unsanitary living conditions in tenements
Your answer is "Letter B, Religious differences increased rivalries between nations".
Trenches sheltered troops from atrillery and machine gun and rifle gire from across no mans land
