Final answer:
American Indian populations were decimated by diseases brought by the Europeans.
Step-by-step explanation:
The contact between Europeans and American Indians resulted in the spread of diseases such as smallpox, influenza, measles, and typhus. European populations had developed resistance to these diseases over time, but Native Americans had no natural immunity. As a result, up to 90 percent of Native Americans died from infectious diseases after the arrival of Europeans.
For example, the Caribbean island of Hispaniola had over a million people in 1492, but by 1548, only 500 natives were left alive. This drastic population decline was due to the virulent spread of diseases.
Therefore, the statement that best describes the effect of the disease is option C: American Indian populations were decimated by diseases brought by the Europeans.