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The South American highlands were a center of early agriculture. Genetic testing of the wide variety of cultivars and wild species suggests that the potato has a single origin in the area of southern Peru, from a species in the Solanum brevicaule complex. Over 99% of all modern cultivated potatoes worldwide are descendants of a subspecies indigenous to south-central Chile, Solanum tuberosum ssp. tuberosum, where it was cultivated as long as 10,000 years ago. According to George Raudzens, "It is clear that in pre-Columbian times some groups struggled to survive and often suffered food shortages and famines, while others enjoyed a varied and substantial diet." The persistent drought around 850 AD coincided with the collapse of Classic Maya civilization, and the famine of One Rabbit (AD 1454) was a major catastrophe in Mexico.
What event in 850 AD coincided with the collapse of Mayan civilization?
A: persistent drought

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Observing that face-to-face communication of the type that online videos convey has been "fine-tuned by millions of years of evolution", TED curator Chris Anderson referred to several YouTube contributors and asserted that "what Gutenberg did for writing, online video can now do for face-to-face communication". Anderson asserted that it's not far-fetched to say that online video will dramatically accelerate scientific advance, and that video contributors may be about to launch "the biggest learning cycle in human history." In education, for example, the Khan Academy grew from YouTube video tutoring sessions for founder Salman Khan's cousin into what Forbes' Michael Noer called "the largest school in the world", with technology poised to disrupt how people learn.
What other surprising aspect of human development will youtube likely have an impact on?
A: education

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Some Europeans living among Indigenous Americans were called "white Indians". They "lived in native communities for years, learned native languages fluently, attended native councils, and often fought alongside their native companions." More numerous and typical were traders and trappers, who married Indigenous American women from tribes on the frontier and had families with them. Some traders, who kept bases in the cities, had what ware called "country wives" among Indigenous Americans, with legal European-American wives and children at home in the city. Not all abandoned their "natural" mixed-race children. Some arranged for sons to be sent to European-American schools for their education.
Why were some multiracial children sent to Europe?
A: for their education

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On 7 April 1963, the country changed its official name to the Socialist Federal Republic of Yugoslavia. Reforms encouraged private enterprise and greatly relaxed restrictions on freedom of speech and religious expression. Tito subsequently went on a tour of the Americas. In Chile, two government ministers resigned over his visit to that country. In the autumn of 1960 Tito met President Dwight D. Eisenhower at the United Nations General Assembly meeting. Tito and Eisenhower discussed a range of issues from arms control to economic development. When Eisenhower remarked that Yugoslavia's neutralism was "neutral on his side", Tito replied that neutralism did not imply passivity but meant "not taking sides".
Who said that neutralism did not imply passivity but mean "not taking sides"?
A:
Tito