Final answer:
The Spanish invaders received assistance from local indigenous tribes that were enemies of the Aztecs, such as the Totonacs and the Tlaxcalans. The unintentional spread of smallpox by the Spanish also played a significant role in the fall of the Aztec Empire. option d is answer
Step-by-step explanation:
The Spanish invaders had the help of local indigenous tribes that were enemies of the Aztecs, such as the Totonacs and the Tlaxcalans. These tribes joined forces with the Spanish and provided them with fighters during the siege of Tenochtitlán. Additionally, unintentional introduction of smallpox into Tenochtitlán by the Spanish resulted in the deaths of thousands of Aztecs, weakening their resistance and contributing to the fall of the Aztec Empire.option d is answer