Answer:
A. It sharply decreased their population.
Step-by-step explanation:
This is the greatest short-term effect of Spanish colonization on American Indians. Colonization brought many negative and positive effects on American Indians, but the most immediate and significant one was a sharp decline in their population. This was due to the diseases that the colonizers carried. As the Native Americans were not resistant to them, many died shortly after their arrival, decimating the population.