Which of the following has a caste system

Which act of the conquistador pizarro was crucial in overthrowing the inca? a. the destruction of the ancient inca city, machu picchu b. the siege of the inca capital near the cuzco valley c. the execution of the last inca ruler, atahualpa d. the unexpected deaths of 3 million inca warriors e. the murder of former inca emperor, huascar

What happened 10 million years ago? if u answer, u get 50 ! plz answer ; -;

The oldest known mesopotamian civilization settled in areas along river banks or sea sides surrounded by mountains and deserts which two statements explain why three geographical features led to the rise of mesopotamian civilizations