Problem: Multiracial American:

In Virginia prior to 1920, for example, a person was legally white if having seven-eights or more white ancestry. The one-drop rule originated in some Southern United States in the late 19th century, likely in response to whites' attempt to maintain white supremacy and limit black political power following the Democrats' regaining control of state legislatures in the late 1870s. The first year in which the U.S. Census dropped the mulatto category was 1920; that year enumerators were instructed to classify people in a binary way as white or black. This was a result of the Southern-dominated Congress convincing the Census Bureau to change its rules.

When was a person legally white in South Carolina before 1920?
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A: unanswerable


Problem: Within hours of the UK and France declaring war on Germany on 3 September 1939, the RAF bombed German warships along the German coast at Wilhelmshaven. Thereafter bombing operations were against ports and shipping and propaganda leaflet drops. Operations were planned to minimize civilian casualties. From 15 May 1940 – the day after the Luftwaffe destroyed the centre of Rotterdam – the RAF also carried out operations east of the Rhine, attacking industrial and transportation targets. Operations were carried out every night thereafter.
Which two countries declared war on Germany on September 3 1939?
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Answer: UK and France


Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
In simple terms the structure of the Alps consists of layers of rock of European, African and oceanic (Tethyan) origin. The bottom nappe structure is of continental European origin, above which are stacked marine sediment nappes, topped off by nappes derived from the African plate. The Matterhorn is an example of the ongoing orogeny and shows evidence of great folding. The tip of the mountain consists of gneisses from the African plate; the base of the peak, below the glaciated area, consists of European basement rock. The sequence of Tethyan marine sediments and their oceanic basement is sandwiched between rock derived from the African and European plates.
Where are the top of the nappes derived from? 
A: the African plate


Context and question: The Baltic Way or Baltic Chain (also Chain of Freedom Estonian: Balti kett, Latvian: Baltijas ceļš, Lithuanian: Baltijos kelias, Russian: Балтийский путь) was a peaceful political demonstration on August 23, 1989. An estimated 2 million people joined hands to form a human chain extending 600 kilometres (370 mi) across Estonia, Latvia and Lithuania, which had been forcibly reincorporated into the Soviet Union in 1944. The colossal demonstration marked the 50th anniversary of the Molotov–Ribbentrop Pact that divided Eastern Europe into spheres of influence and led to the occupation of the Baltic states in 1940.
What states did the chain extend over?
Answer: Estonia, Latvia and Lithuania


Question: Semi-additive is the most common process: The unpatterned board has a thin layer of copper already on it. A reverse mask is then applied. (Unlike a subtractive process mask, this mask exposes those parts of the substrate that will eventually become the traces.) Additional copper is then plated onto the board in the unmasked areas; copper may be plated to any desired weight. Tin-lead or other surface platings are then applied. The mask is stripped away and a brief etching step removes the now-exposed bare original copper laminate from the board, isolating the individual traces. Some single-sided boards which have plated-through holes are made in this way. General Electric made consumer radio sets in the late 1960s using additive boards.
Is there an answer to this question: The patterned board has a thin layer of what already on it?

Answer: unanswerable


Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
Following the war, some of these military airfields added civil facilities for handling passenger traffic. One of the earliest such fields was Paris – Le Bourget Airport at Le Bourget, near Paris. The first airport to operate scheduled international commercial services was Hounslow Heath Aerodrome in August 1919, but it was closed and supplanted by Croydon Airport in March 1920. In 1922, the first permanent airport and commercial terminal solely for commercial aviation was opened at Flughafen Devau near what was then Königsberg, East Prussia. The airports of this era used a paved "apron", which permitted night flying as well as landing heavier aircraft.
What was the first airport to operate scheduled international commercial services?
A:
Hounslow Heath Aerodrome