Here is a question about this article: In the early 20th century, Carl von Voit and Max Rubner independently measured caloric energy expenditure in different species of animals, applying principles of physics in nutrition. In 1906, Edith G. Willcock and Frederick Hopkins showed that the amino acid tryptophan aids the well-being of mice but it did not assure their growth. In the middle of twelve years of attempts to isolate them, Hopkins said in a 1906 lecture that "unsuspected dietetic factors," other than calories, protein, and minerals, are needed to prevent deficiency diseases. In 1907, Stephen M. Babcock and Edwin B. Hart conducted the single-grain experiment, which took nearly four years to complete.
What is the answer to this question: Which experiment related to diet was conducted that required four years to complete?
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So... single-grain experiment

Here is a question about this article: The diversion of heavier bombers to the Balkans meant that the crews and units left behind were asked to fly two or three sorties per night. Bombers were noisy, cold, and vibrated badly. Added to the tension of the mission which exhausted and drained crews, tiredness caught up with and killed many. In one incident on 28/29 April, Peter Stahl of KG 30 was flying on his 50th mission. He fell asleep at the controls of his Ju 88 and woke up to discover the entire crew asleep. He roused them, ensured they took oxygen and Dextro-Energen tablets, then completed the mission.
What is the answer to this question: What did Peter's crew take to complete their mission?
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So... oxygen and Dextro-Energen tablets

Here is a question about this article: Whittaker was unsuited for the role and soon retired. Stewart and Harlan were conservative Republicans, while Brennan was a Democrat who became a leading voice for liberalism. In selecting a Chief Justice, Eisenhower looked for an experienced jurist who could appeal to liberals in the party as well as law-and-order conservatives, noting privately that Warren "represents the kind of political, economic, and social thinking that I believe we need on the Supreme Court ... He has a national name for integrity, uprightness, and courage that, again, I believe we need on the Court". In the next few years Warren led the Court in a series of liberal decisions that revolutionized the role of the Court.
What is the answer to this question: Who did Eisenhower nominate for Chief Justice?
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So...
Warren