Final answer:
The Maya fell due to internal forces including environmental problems and social unrest, while the Aztec and Inca were conquered by external forces—Spanish invaders who utilized advanced technology, formed alliances with other tribes, and brought diseases.
Step-by-step explanation:
The reasons for the fall of the Maya, Aztec, and Inca civilizations were different. The fall of the Maya was due to a mixture of internal forces including environmental changes, warfare among city-states, and possibly social unrest. Climate change and demographic growth led to deforestation and soil erosion, affecting agriculture and putting pressure on society.
In contrast, the Aztec and Inca empires fell primarily due to external forces. The Aztecs were conquered by the Spanish in 1521, abetted by internal dissent from tributary states and a smallpox epidemic. Similarly, the Inca were overwhelmed by Spanish invaders led by Pizarro, coupled with internal conflicts following a recent civil war. The correct answer to the student's question is c) The fall of the Maya was caused by internal forces while the fall of the Aztec and Inca were caused by external forces.