Problem: Mandolin:

Mandolin has also been used in blues music, most notably by Ry Cooder, who performed outstanding covers on his very first recordings, Yank Rachell, Johnny "Man" Young, Carl Martin, and Gerry Hundt. Howard Armstrong, who is famous for blues violin, got his start with his father's mandolin and played in string bands similar to the other Tennessee string bands he came into contact with, with band makeup including "mandolins and fiddles and guitars and banjos. And once in a while they would ease a little ukulele in there and a bass fiddle." Other blues players from the era's string bands include Willie Black (Whistler And His Jug Band), Dink Brister, Jim Hill, Charles Johnson, Coley Jones (Dallas String Band), Bobby Leecan (Need More Band), Alfred Martin, Charlie McCoy (1909-1950), Al Miller, Matthew Prater, and Herb Quinn.

Who played in the Whistler and His Jug Band?
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A: Willie Black

Problem: Eritrea:

Eritrea is a member of the United Nations, the African Union, and is an observing member of the Arab League. The nation holds a seat on the United Nations' Advisory Committee on Administrative and Budgetary Questions (ACABQ). Eritrea also holds memberships in the International Bank for Reconstruction and Development, International Finance Corporation, International Criminal Police Organization (INTERPOL), Non-Aligned Movement, Organization for the Prohibition of Chemical Weapons, Permanent Court of Arbitration, and the World Customs Organization.

Which league is Eritrea an observing member of?
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A: Arab League

Problem: Great Plains:

The rural Plains have lost a third of their population since 1920. Several hundred thousand square miles (several hundred thousand square kilometers) of the Great Plains have fewer than 6 inhabitants per square mile (2.3 inhabitants per square kilometer)the density standard Frederick Jackson Turner used to declare the American frontier "closed" in 1893. Many have fewer than 2 inhabitants per square mile (0.77 inhabitants per square kilometer). There are more than 6,000 ghost towns in the state of Kansas alone, according to Kansas historian Daniel Fitzgerald. This problem is often exacerbated by the consolidation of farms and the difficulty of attracting modern industry to the region. In addition, the smaller school-age population has forced the consolidation of school districts and the closure of high schools in some communities. The continuing population loss has led some to suggest that the current use of the drier parts of the Great Plains is not sustainable, and there has been a proposal - the "Buffalo Commons" - to return approximately 139,000 square miles (360,000 km2) of these drier parts to native prairie land.

In what year was the Great Plains considered "open" to inhabitants and farm activity?
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A: unanswerable

Problem: Catalan language:

With the union of the crowns of Castille and Aragon (1479), the use of Spanish gradually became more prestigious. Starting in the 16th century, Catalan literature experienced a decline, the language came under the influence of Spanish, and the urban and literary classes became bilingual.

When did Catalan literature begin a downward trend?
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A:
16th century