Problem: Thuringia:

The Thuringian Realm existed until 531 and later, the Landgraviate of Thuringia was the largest state in the region, persisting between 1131 and 1247. Afterwards there was no state named Thuringia, nevertheless the term commonly described the region between the Harz mountains in the north, the Weie Elster river in the east, the Franconian Forest in the south and the Werra river in the west. After the Treaty of Leipzig, Thuringia had its own dynasty again, the Ernestine Wettins. Their various lands formed the Free State of Thuringia, founded in 1920, together with some other small principalities. The Prussian territories around Erfurt, Muhlhausen and Nordhausen joined Thuringia in 1945.

Where is Thuringia formerly located?
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A: unanswerable

Problem: Houston:

In 2013, Houston was identified as the #1 U.S. city for job creation by the U.S. Bureau of Statistics after it was not only the first major city to regain all the jobs lost in the preceding economic downturn, but after the crash, more than two jobs were added for every one lost. Economist and vice president of research at the Greater Houston Partnership Patrick Jankowski attributed Houston's success to the ability of the region's real estate and energy industries to learn from historical mistakes. Furthermore, Jankowski stated that "more than 100 foreign-owned companies relocated, expanded or started new businesses in Houston" between 2008 and 2010, and this openness to external business boosted job creation during a period when domestic demand was problematically low. Also in 2013, Houston again appeared on Forbes' list of Best Places for Business and Careers.

How many jobs did Houston add for every one lost?
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A: two

Problem: Economy of Greece:

The evolution of the Greek economy during the 19th century (a period that transformed a large part of the world because of the Industrial Revolution) has been little researched. Recent research from 2006 examines the gradual development of industry and further development of shipping in a predominantly agricultural economy, calculating an average rate of per capita GDP growth between 1833 and 1911 that was only slightly lower than that of the other Western European nations. Industrial activity, (including heavy industry like shipbuilding) was evident, mainly in Ermoupolis and Piraeus. Nonetheless, Greece faced economic hardships and defaulted on its external loans in 1826, 1843, 1860 and 1894.

What does recent research from 2006 examine?
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A: evolution of the Greek economy

Problem: Computer security:

One use of the term "computer security" refers to technology that is used to implement secure operating systems. In the 1980s the United States Department of Defense (DoD) used the "Orange Book" standards, but the current international standard ISO/IEC 15408, "Common Criteria" defines a number of progressively more stringent Evaluation Assurance Levels. Many common operating systems meet the EAL4 standard of being "Methodically Designed, Tested and Reviewed", but the formal verification required for the highest levels means that they are uncommon. An example of an EAL6 ("Semiformally Verified Design and Tested") system is Integrity-178B, which is used in the Airbus A380 and several military jets.

What makes it difficult for systems to use the EAL4 standard?
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A:
unanswerable