Final answer:
The Spanish conquistadors defeated the Aztecs through superior weapons, alliances with other native tribes, and the inadvertent introduction of smallpox. The option (A) is correct.
Step-by-step explanation:
The Spanish conquistadors beat the Aztecs through a combination of superior weapons and alliances with other native tribes. The Spanish soldiers had steel armor, steel swords, and the advantage of attacking on horseback, while the Aztecs fought with bows, arrows, and spears.
Additionally, the Spanish found unexpected allies in tribes that were previously forced to pay tribute to the Aztec Empire. One such group, the Totonacs, greeted the Spanish as liberators. Another factor that contributed to the Spanish victory was the inadvertent introduction of smallpox into Tenochtitlan, resulting in the deaths of thousands. Therefore, option (A) is correct.