Problem: European colonists created treaties with Indigenous American tribes requesting the return of any runaway slaves. For example, in 1726, the British governor of New York exacted a promise from the Iroquois to return all runaway slaves who had joined them. This same promise was extracted from the Huron Nation in 1764, and from the Delaware Nation in 1765, though there is no record of slaves ever being returned. Numerous advertisements requested the return of African Americans who had married Indigenous Americans or who spoke an Indigenous American language. The primary exposure that Africans and Indigenous Americans had to each other came through the institution of slavery. Indigenous Americans learned that Africans had what Indigenous Americans considered 'Great Medicine' in their bodies because Africans were virtually immune to the Old-World diseases that were decimating most native populations. Because of this, many tribes encouraged marriage between the two groups, to create stronger, healthier children from the unions.
Why did the tribes encourage marriage between Indigenous Americans and whites?
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Answer: unanswerable

Problem: Since incandescent light bulbs use more energy than alternatives such as CFLs and LED lamps, many governments have introduced measures to ban their use, by setting minimum efficacy standards higher than can be achieved by incandescent lamps. Measures to ban light bulbs have been implemented in the European Union, the United States, Russia, Brazil, Argentina, Canada and Australia, among others. In the Europe the EC has calculated that the ban contributes 5 to 10 billion euros to the economy and saves 40 TWh of electricity every year, translating in CO2 emission reductions of 15 million tonnes.
What type of light bulbs use less energy than alternatives?
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Answer: unanswerable

Problem: An in-depth study of MP3 audio quality, sound artist and composer Ryan Maguire's project "The Ghost in the MP3" isolates the sounds lost during MP3 compression. In 2015, he released the track "moDernisT" (an anagram of "Tom's Diner"), composed exclusively from the sounds deleted during MP3 compression of the song "Tom's Diner", the track originally used in the formulation of the MP3 standard. A detailed account of the techniques used to isolate the sounds deleted during MP3 compression, along with the conceptual motivation for the project, was published in the 2014 Proceedings of the International Computer Music Conference.
What did the study aim to isolate?
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Answer:
sounds lost during MP3 compression