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Commercial solar water heaters began appearing in the United States in the 1890s. These systems saw increasing use until the 1920s but were gradually replaced by cheaper and more reliable heating fuels. As with photovoltaics, solar water heating attracted renewed attention as a result of the oil crises in the 1970s but interest subsided in the 1980s due to falling petroleum prices. Development in the solar water heating sector progressed steadily throughout the 1990s and growth rates have averaged 20% per year since 1999. Although generally underestimated, solar water heating and cooling is by far the most widely deployed solar technology with an estimated capacity of 154 GW as of 2007.
Since 1999, what average rate has the solar water heating sector progressed at?
A: 20% per year

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The Section d'Or, also known as Groupe de Puteaux, founded by some of the most conspicuous Cubists, was a collective of painters, sculptors and critics associated with Cubism and Orphism, active from 1911 through about 1914, coming to prominence in the wake of their controversial showing at the 1911 Salon des Independants. The Salon de la Section d'Or at the Galerie La Boetie in Paris, October 1912, was arguably the most important pre-World War I Cubist exhibition; exposing Cubism to a wide audience. Over 200 works were displayed, and the fact that many of the artists showed artworks representative of their development from 1909 to 1912 gave the exhibition the allure of a Cubist retrospective.
How many works displayed at The Salon de la Section d'Or at the Galerie La Boetie in Paris, October 1922?
A: unanswerable

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At the time of the Roman Empire, about two thousand years ago, various tribes, which spoke Celtic dialects of the Insular Celtic group, were inhabiting the islands. The Romans expanded their civilisation to control southern Great Britain but were impeded in advancing any further, building Hadrian's Wall to mark the northern frontier of their empire in 122 AD. At that time, Ireland was populated by a people known as Hiberni, the northern third or so of Great Britain by a people known as Picts and the southern two thirds by Britons.
The people that lived in the British Isles during the Roman Empire era spoke which language?
A: Celtic dialects of the Insular Celtic group

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Most British pubs still have decorated signs hanging over their doors, and these retain their original function of enabling the identification of the pub. Today's pub signs almost always bear the name of the pub, both in words and in pictorial representation. The more remote country pubs often have stand-alone signs directing potential customers to their door.
What purpose do stand-alone signs serve for country pubs?
A:
directing potential customers to their door