Problem: Uranium:

Uranium-238 is the most stable isotope of uranium, with a half-life of about 4.468109 years, roughly the age of the Earth. Uranium-235 has a half-life of about 7.13108 years, and uranium-234 has a half-life of about 2.48105 years. For natural uranium, about 49% of its alpha rays are emitted by each of 238U atom, and also 49% by 234U (since the latter is formed from the former) and about 2.0% of them by the 235U. When the Earth was young, probably about one-fifth of its uranium was uranium-235, but the percentage of 234U was probably much lower than this.

What percentage of the gamma rays of natural uranium are emitted by 234U?
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A: unanswerable

Problem: A second New Haven gastronomical claim to fame is Louis' Lunch, which is located in a small brick building on Crown Street and has been serving fast food since 1895. Though fiercely debated, the restaurant's founder Louis Lassen is credited by the Library of Congress with inventing the hamburger and steak sandwich. Louis' Lunch broils hamburgers, steak sandwiches and hot dogs vertically in original antique 1898 cast iron stoves using gridirons, patented by local resident Luigi Pieragostini in 1939, that hold the meat in place while it cooks.
Louis' Lunch is popular for serving what?
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Answer: the hamburger

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
The Classical era stringed instruments were the four instruments which form the string section of the orchestra: the violin, viola, cello and contrabass. Woodwinds included the basset clarinet, basset horn, clarinette d'amour, the Classical clarinet, the chalumeau, the flute, oboe and bassoon. Keyboard instruments included the clavichord and the fortepiano. While the harpsichord was still used in basso continuo accompaniment in the 1750s and 1760s, it fell out of use in the end of the century. Brass instruments included the buccin, the ophicleide (a serpent replacement which was the precursor of tuba) and the natural horn.
What instrument was the precursor of the tuba?
A: the ophicleide

Context and question: Comparative and historical linguistics offers some clues for memorising the accent position: If one compares many standard Serbo-Croatian words to e.g. cognate Russian words, the accent in the Serbo-Croatian word will be one syllable before the one in the Russian word, with the rising tone. Historically, the rising tone appeared when the place of the accent shifted to the preceding syllable (the so-called "Neoshtokavian retraction"), but the quality of this new accent was different its melody still "gravitated" towards the original syllable. Most Shtokavian dialects (Neoshtokavian) dialects underwent this shift, but Chakavian, Kajkavian and the Old Shtokavian dialects did not.
What offers some clues for how dialects were different?
Answer: unanswerable

Question: In 1822, the American Colonization Society began sending African-American volunteers to the Pepper Coast to establish a colony for freed African Americans. By 1867, the ACS (and state-related chapters) had assisted in the migration of more than 13,000 African Americans to Liberia. These free African Americans and their descendants married within their community and came to identify as Americo-Liberians. Many were of mixed race and educated in American culture; they did not identify with the indigenous natives of the tribes they encountered. They intermarried largely within the colonial community, developing an ethnic group that had a cultural tradition infused with American notions of political republicanism and Protestant Christianity.
Is there an answer to this question: What did African Americans moved to Liberia keep from America?

Answer: cultural tradition

QUES: Assembly of desktop computers for the North American market formerly took place at Dell plants in Austin, Texas (original location) and Lebanon, Tennessee (opened in 1999), which have been closed in 2008 and early 2009, respectively. The plant in Winston-Salem, North Carolina received $280 million USD in incentives from the state and opened in 2005, but ceased operations in November 2010, and Dell's contract with the state requires them to repay the incentives for failing to meet the conditions. Most of the work that used to take place in Dell's U.S. plants was transferred to contract manufacturers in Asia and Mexico, or some of Dell's own factories overseas. The Miami, Florida facility of its Alienware subsidiary remains in operation, while Dell continues to produce its servers (its most profitable products) in Austin, Texas.

What year was Dell's Tennessee facility closed?
What is the answer?
ANS:
unanswerable