Problem: Arsenal F.C.:

There have always been Arsenal supporters outside London, and since the advent of satellite television, a supporter's attachment to a football club has become less dependent on geography. Consequently, Arsenal have a significant number of fans from beyond London and all over the world; in 2007, 24 UK, 37 Irish and 49 other overseas supporters clubs were affiliated with the club. A 2011 report by SPORT+MARKT estimated Arsenal's global fanbase at 113 million. The club's social media activity was the fifth highest in world football during the 2014–15 season.

In what year did SPORT+MARKT start printing?
---
A: unanswerable


Problem: Copyright infringement:

The first criminal provision in U.S. copyright law was added in 1897, which established a misdemeanor penalty for "unlawful performances and representations of copyrighted dramatic and musical compositions" if the violation had been "willful and for profit." Criminal copyright infringement requires that the infringer acted "for the purpose of commercial advantage or private financial gain." 17 U.S.C. § 506. To establish criminal liability, the prosecutor must first show the basic elements of copyright infringement: ownership of a valid copyright, and the violation of one or more of the copyright holder's exclusive rights. The government must then establish that defendant willfully infringed or, in other words, possessed the necessary mens rea. Misdemeanor infringement has a very low threshold in terms of number of copies and the value of the infringed works.

What type of penalty was made for lawful performances that are willful and for profit?
---
A: unanswerable


Problem: Classical music:

Although Classical music in the 2000s has lost most of its tradition for musical improvisation, from the Baroque era to the Romantic era, there are examples of performers who could improvise in the style of their era. In the Baroque era, organ performers would improvise preludes, keyboard performers playing harpsichord would improvise chords from the figured bass symbols beneath the bass notes of the basso continuo part and both vocal and instrumental performers would improvise musical ornaments. J.S. Bach was particularly noted for his complex improvisations. During the Classical era, the composer-performer Mozart was noted for his ability to improvise melodies in different styles. During the Classical era, some virtuoso soloists would improvise the cadenza sections of a concerto. During the Romantic era, Beethoven would improvise at the piano. For more information, see Improvisation.

What was Mozart noted for?
---
A: his ability to improvise melodies in different styles


Problem: Translation:

When a historic document survives only in translation, the original having been lost, researchers sometimes undertake back-translation in an effort to reconstruct the original text. An example involves the novel The Saragossa Manuscript by the Polish aristocrat Jan Potocki (1761–1815), who wrote the novel in French and anonymously published fragments in 1804 and 1813–14. Portions of the original French-language manuscript were subsequently lost; however, the missing fragments survived in a Polish translation that was made by Edmund Chojecki in 1847 from a complete French copy, now lost. French-language versions of the complete Saragossa Manuscript have since been produced, based on extant French-language fragments and on French-language versions that have been back-translated from Chojecki’s Polish version.

What do researchers use back-translation to try to reconstruct when a document survives only in translation?
---
A:
the original text