How did the incas the city in the clouds

The Incas called it Qosqo, the center of the world. Today, Cuzco is a center of world tourism, drawing more than 300,000 visitors a year to the former imperial capital, a unique blend of unparalleled pre-Colombian stonemasonry and colonial architecture.

Although Peru has made more headlines recently for coup d'tats and a drawn-out guerrilla war, Cuzco and the nearby Inca citadel of Machu Picchu have never ceased to be one of South America's premier attractions.

Peru gave rise to many highly advanced civilizations stretching back well before 2000 B.C., but none was quite as innovative as the Incas'.

Explanation:

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answer; i believe the correct answer is (a) the correlation between the cause variable and outcome variable is zero;

what is the other part to the question