The problem: Answer a question about this article:
Spring and autumn have, on average, mild days and fresh nights but are changing and unstable. Surprisingly warm or cool weather occurs frequently in both seasons. In winter, sunshine is scarce; days are cold but generally above freezing with temperatures around 7 °C (45 °F). Light night frosts are however quite common, but the temperature will dip below −5 °C (23 °F) for only a few days a year. Snow falls every year, but rarely stays on the ground. The city sometimes sees light snow or flurries with or without accumulation.
Does Paris see snow?
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The answer: sometimes sees light snow or flurries


The problem: Answer a question about this article:
Motors have very little room for electrical insulation so they generally have low voltage ratings. Because transformers (prior to the development of power electronics) cannot step down DC voltages, trains were supplied with a relatively low DC voltage that the motors can use directly. The most common DC voltages are listed in the previous section. Third (and fourth) rail systems almost always use voltages below 1 kV for safety reasons while overhead wires usually use higher voltages for efficiency. ("Low" voltage is relative; even 600 V can be instantly lethal when touched.)
Why 1kV voltage is almost always used by rail systems?
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The answer: safety reasons


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Bitumen was the nemesis of many artists during the 19th century. Although widely used for a time, it ultimately proved unstable for use in oil painting, especially when mixed with the most common diluents, such as linseed oil, varnish and turpentine. Unless thoroughly diluted, bitumen never fully solidifies and will in time corrupt the other pigments with which it comes into contact. The use of bitumen as a glaze to set in shadow or mixed with other colors to render a darker tone resulted in the eventual deterioration of many paintings, for instance those of Delacroix. Perhaps the most famous example of the destructiveness of bitumen is Théodore Géricault's Raft of the Medusa (1818–1819), where his use of bitumen caused the brilliant colors to degenerate into dark greens and blacks and the paint and canvas to buckle.
What major problem did bitumen as a pigment show itself to be?  
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The answer: unstable


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The family of instruments used, especially in orchestras, grew. A wider array of percussion instruments began to appear. Brass instruments took on larger roles, as the introduction of rotary valves made it possible for them to play a wider range of notes. The size of the orchestra (typically around 40 in the Classical era) grew to be over 100. Gustav Mahler's 1906 Symphony No. 8, for example, has been performed with over 150 instrumentalists and choirs of over 400.
What size orchestras have performed Gustav Mahler's 1906 Symphony No. 8?
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The answer:
over 150