For which of the following major world events has the spread of disease been a negative effect?

The technological revolution B. mapping the European world Colombian Exchange Reform

The Columbian Exchange, though a highly lucrative trade route, was a direct source of hardship for many peoples. Native Americans, for example, had their populations decimated by diseases to which they had no immunity. Whole communities were wiped off the map, those that remained were too small in number to halt the colonization efforts of the European powers.