C) Contagious diseases spread to both Europe and the Americas
Explanation:
The Columbian Exchange had many positives for both sides of the Atlantic, but unfortunately it had some negatives too. The biggest negatives were the spreading out of diseases. Both in Europe and the Americas, multiple diseases were brought from the other side, and they had devastating effects. The Europeans were affected but not to a degree to become almost extinct, while the Native Americans almost died out totally because of the diseases brought by the Europeans.
