Problem: Slavs:

Proto-Slavic, the supposed ancestor language of all Slavic languages, is a descendant of common Proto-Indo-European, via a Balto-Slavic stage in which it developed numerous lexical and morphophonological isoglosses with the Baltic languages. In the framework of the Kurgan hypothesis, "the Indo-Europeans who remained after the migrations [from the steppe] became speakers of Balto-Slavic".

Who became speakers of Balto-Slavic?
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A: Indo-Europeans


Problem: Allied submarines did not adopt a defensive posture and wait for the enemy to attack. Within hours after the Pearl Harbor attack, in retribution against Japan, Roosevelt promulgated a new doctrine: unrestricted submarine warfare against Japan. This meant sinking any warship, commercial vessel, or passenger ship in Axis-controlled waters, without warning and without help to survivors.[nb 13] At the outbreak of the war in the Pacific the Dutch Admiral in charge of the naval defense of the East Indies, Conrad Helfrich, gave instructions to wage war aggressively. His small force of submarines sank more Japanese ships in the first weeks of the war than the entire British and US navies together, an exploit which earned him the nickname "Ship-a-day Helfrich". The Dutch force were in fact the first to sink an enemy warship; On 24 December 1941, HNLMS K XVI torpedoed and sank the Japanese destroyer Sagiri.
When was the first Japanese warship sunk by a submarine?
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Answer: 24 December 1941


Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
In astronomy, Muḥammad ibn Jābir al-Ḥarrānī al-Battānī improved the precision of the measurement of the precession of the Earth's axis. The corrections made to the geocentric model by al-Battani, Averroes, Nasir al-Din al-Tusi, Mu'ayyad al-Din al-'Urdi and Ibn al-Shatir were later incorporated into the Copernican heliocentric model. Heliocentric theories were also discussed by several other Muslim astronomers such as Al-Biruni, Al-Sijzi, Qotb al-Din Shirazi, and Najm al-Dīn al-Qazwīnī al-Kātibī. The astrolabe, though originally developed by the Greeks, was perfected by Islamic astronomers and engineers, and was subsequently brought to Europe.
Who perfected the astrolabe originally developed by Islamic astronomers?
A: unanswerable


Context and question: IMF's forecast said that Greece's unemployment rate would hit the highest 14.8 percent in 2012 and decrease to 14.1 in 2014.  But in fact, the Greek economy suffered a prolonged high unemployemnt. The unemployment figure was between 9 per cent and 11 per cent in 2009, and it soared to 28 per cent in 2013. In 2015, Greece's jobless rate is around 24 per cent. It is thought that Greece's potential output has been eroded by this prolonged massive unemployment due to the associated hysteresis effects.
What did Greece's unemployment rate crash to in 2013?
Answer: unanswerable


Question: Since June 2007, YouTube's videos have been available for viewing on a range of Apple products. This required YouTube's content to be transcoded into Apple's preferred video standard, H.264, a process that took several months. YouTube videos can be viewed on devices including Apple TV, iPod Touch and the iPhone. In July 2010, the mobile version of the site was relaunched based on HTML5, avoiding the need to use Adobe Flash Player and optimized for use with touch screen controls. The mobile version is also available as an app for the Android platform. In September 2012, YouTube launched its first app for the iPhone, following the decision to drop YouTube as one of the preloaded apps in the iPhone 5 and iOS 6 operating system. According to GlobalWebIndex, YouTube was used by 35% of smartphone users between April and June 2013, making it the third most used app.
Is there an answer to this question: What is Apple's prefered video standard?

Answer: H.264


Problem: Mandolin:

Phil Skinner played a key role in 20th century development of the mandolin movement in Australia, and was awarded an MBE in 1979 for services to music and the community. He was born Harry Skinner in Sydney in 1903 and started learning music at age 10 when his uncle tutored him on the banjo. Skinner began teaching part-time at age 18, until the Great Depression forced him to begin teaching full-time and learn a broader range of instruments. Skinner founded the Sydney Mandolin Orchestra, the oldest surviving mandolin orchestra in Australia.

 At what age did Phil Skinner stop playing music?
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A:
unanswerable