The correct responses that led to the decline of the Inca Empire are:
- Disease and civil war ravaged the Inca Empire.
- Pizarro took Atahualpa hostage and then had him executed.
The other options are not accurate representations of events that contributed to the decline of the Inca Empire. The Inca did not systematically kill every Spaniard they encountered, and while the Spanish did use tactics of deception, they did not primarily send messages of peace and friendship. Pizarro's expedition and the capture and execution of Atahualpa were significant factors in the downfall of the empire.