What effect did the introduction of smallpox have in the americas?
a. it contributed to the defeat of american indians.
b. it led to large numbers of deaths among european colonists in the americas.
c. it allowed american indians to quickly develop a resistance to the disease.
d. it resulted in the inability of europeans to establish colonies in the americas.

The correct answer is A. The introduction of smallpox in the Americas contributed to the defeat of American Indians.

Explanation:

Smallpox was caused by the variola virus that emerged in human populations around the year 10,000 BC. For several centuries, successive epidemics devastated the population, as the mortality rate of the disease was as high as 30% of infected patients.

After affecting the Old World for centuries, during the Conquest of the Americas it was infected by the newcomers to the Native Indians, who totally lacked of defenses against this disease unknown to them, causing a demographic collapse in the native populations. In 1520, it appeared among the Aztecs during the siege of Tenochtitlan, also provoking the death of the Aztec leader Cuitlahuac. Among the Incas the smallpox killed the monarch Huayna Capac and caused a demographic disaster in the Tahuantinsuyo, which before the arrival of the Spaniards had 14 million inhabitants, while by the eighteenth century it had only 1.5 million. In Chile, it stopped the advance of the Mapuche after the death of Valdivia.