Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
Pitch is an auditory sensation in which a listener assigns musical tones to relative positions on a musical scale based primarily on their perception of the frequency of vibration. Pitch is closely related to frequency, but the two are not equivalent. Frequency is an objective, scientific attribute that can be measured. Pitch is each person's subjective perception of a sound, which cannot be directly measured. However, this does not necessarily mean that most people won't agree on which notes are higher and lower.
What type of sensation is pitch?
A: auditory

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Built around 1915, the Alaska Railroad (ARR) played a key role in the development of Alaska through the 20th century. It links north Pacific shipping through providing critical infrastructure with tracks that run from Seward to Interior Alaska by way of South Central Alaska, passing through Anchorage, Eklutna, Wasilla, Talkeetna, Denali, and Fairbanks, with spurs to Whittier, Palmer and North Pole. The cities, towns, villages, and region served by ARR tracks are known statewide as "The Railbelt". In recent years, the ever-improving paved highway system began to eclipse the railroad's importance in Alaska's economy.
Which development in 1951 played a key role in developing Alaska?
A: unanswerable

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The motif of the England national football team has three lions passant guardant, the emblem of King Richard I, who reigned from 1189 to 1199. The lions, often blue, have had minor changes to colour and appearance. Initially topped by a crown, this was removed in 1949 when the FA was given an official coat of arms by the College of Arms; this introduced ten Tudor roses, one for each of the regional branches of the FA. Since 2003, England top their logo with a star to recognise their World Cup win in 1966; this was first embroidered onto the left sleeve of the home kit, and a year later was moved to its current position, first on the away shirt.
In what year was the College of Arms established?
A: unanswerable

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The ESA requires that critical habitat be designated at the time of or within one year of a species being placed on the endangered list. In practice, most designations occur several years after listing. Between 1978 and 1986 the FWS regularly designated critical habitat. In 1986 the Reagan Administration issued a regulation limiting the protective status of critical habitat. As a result, few critical habitats were designated between 1986 and the late 1990s. In the late 1990s and early 2000s, a series of court orders invalidated the Reagan regulations and forced the FWS and NMFS to designate several hundred critical habitats, especially in Hawaii, California and other western states. Midwest and Eastern states received less critical habitat, primarily on rivers and coastlines. As of December, 2006, the Reagan regulation has not yet been replaced though its use has been suspended. Nonetheless, the agencies have generally changed course and since about 2005 have tried to designate critical habitat at or near the time of listing.
What is the time limit for designating a species critical habitat after the species has been added to the endangered list?
A:
within one year