Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
The uses of copper in art were not limited to currency: it was used by Renaissance sculptors, in photographic technology known as the daguerreotype, and the Statue of Liberty. Copper plating and copper sheathing for ships' hulls was widespread; the ships of Christopher Columbus were among the earliest to have this feature. The Norddeutsche Affinerie in Hamburg was the first modern electroplating plant starting its production in 1876. The German scientist Gottfried Osann invented powder metallurgy in 1830 while determining the metal's atomic mass; around then it was discovered that the amount and type of alloying element (e.g., tin) to copper would affect bell tones. Flash smelting was developed by Outokumpu in Finland and first applied at Harjavalta in 1949; the energy-efficient process accounts for 50% of the world's primary copper production.
What is the magical technology that uses copper called?
A: unanswerable

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Jordanes tells us that the Sclaveni had swamps and forests for their cities. Another 6th-century source refers to them living among nearly impenetrable forests, rivers, lakes, and marshes.
Who could not penetrate the forests and rivers?
A: unanswerable

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Changes also took place within the recruitment and composition of armies. The use of the national or feudal levy was gradually replaced by paid troops of domestic retinues or foreign mercenaries. The practice was associated with Edward III of England and the condottieri of the Italian city-states. All over Europe, Swiss soldiers were in particularly high demand. At the same time, the period also saw the emergence of the first permanent armies. It was in Valois France, under the heavy demands of the Hundred Years' War, that the armed forces gradually assumed a permanent nature.
Which conflict in France resulted in the establishment of permanent armies?
A: Hundred Years' War

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The term Appalachian refers to several different regions associated with the mountain range. Most broadly, it refers to the entire mountain range with its surrounding hills and the dissected plateau region. The term is often used more restrictively to refer to regions in the central and southern Appalachian Mountains, usually including areas in the states of Kentucky, Tennessee, Virginia, Maryland, West Virginia, and North Carolina, as well as sometimes extending as far south as northern Alabama, Georgia and western South Carolina, and as far north as Pennsylvania, southern Ohio and parts of southern upstate New York.
Which southern states are not referred to in the more restrictive understanding of Appalachian?
A:
unanswerable