Problem: Given the question: Extract the answer to the question from the following context. Question: what is the second time period mentioned? Context: In 1931, RCA Victor introduced their vinyl-based Victrolac compound as a material for some unusual-format and special-purpose records. By the end of the 1930s vinyl's advantages of light weight, relative unbreakability and low surface noise had made it the material of choice for prerecorded radio programming and other critical applications. When it came to ordinary 78 rpm records, however, the much higher cost of the raw material, as well as its vulnerability to the heavy pickups and crudely mass-produced steel needles still commonly used in home record players, made its general substitution for shellac impractical at that time. During the Second World War, the United States Armed Forces produced thousands of 12-inch vinyl 78 rpm V-Discs for use by the troops overseas. After the war, the wider use of vinyl became more practical as new record players with relatively lightweight crystal pickups and precision-ground styli made of sapphire or an exotic osmium alloy proliferated. In late 1945, RCA Victor began offering special transparent red vinyl De Luxe pressings of some classical 78s, at a de luxe price. Later, Decca Records introduced vinyl Deccalite 78s, while other record companies came up with vinyl concoctions such as Metrolite, Merco Plastic and Sav-o-flex, but these were mainly used to produce "unbreakable" children's records and special thin vinyl DJ pressings for shipment to radio stations.
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The answer is:
end of the 1930s

Problem: Given the question: Extract the answer to the question from the following context. Question: Which of the following is not a city: Pomerania, Leiden or Von Kleist? Context: In October 1745, Ewald Georg von Kleist of Pomerania, Germany, found that charge could be stored by connecting a high-voltage electrostatic generator by a wire to a volume of water in a hand-held glass jar. Von Kleist's hand and the water acted as conductors, and the jar as a dielectric (although details of the mechanism were incorrectly identified at the time). Von Kleist found that touching the wire resulted in a powerful spark, much more painful than that obtained from an electrostatic machine. The following year, the Dutch physicist Pieter van Musschenbroek invented a similar capacitor, which was named the Leyden jar, after the University of Leiden where he worked. He also was impressed by the power of the shock he received, writing, "I would not take a second shock for the kingdom of France."
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The answer is:
Von Kleist

Problem: Given the question: Extract the answer to the question from the following context. Question: What is imperfective psat? Context: The verbs of most aspect pairs differ in one of two ways: by prefix or by suffix. In prefix pairs, the perfective verb has an added prefixfor example, the imperfective psat (to write, to be writing) compared with the perfective napsat (to write down, to finish writing). The most common prefixes are na-, o-, po-, s-, u-, vy-, z- and za-. In suffix pairs, a different infinitive ending is added to the perfective stem; for example, the perfective verbs koupit (to buy) and prodat (to sell) have the imperfective forms kupovat and prodavat. Imperfective verbs may undergo further morphology to make other imperfective verbs (iterative and frequentative forms), denoting repeated or regular action. The verb jit (to go) has the iterative form chodit (to go repeatedly) and the frequentative form chodivat (to go regularly).
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The answer is:
to write, to be writing