Extract the answer to the question from the following context. Question: Whay is repetition pitch? Context: It is still possible for two sounds of indefinite pitch to clearly be higher or lower than one another. For instance, a snare drum sounds higher pitched than a bass drum though both have indefinite pitch, because its sound contains higher frequencies. In other words, it is possible and often easy to roughly discern the relative pitches of two sounds of indefinite pitch, but sounds of indefinite pitch do not neatly correspond to any specific pitch. A special type of pitch often occurs in free nature when sound reaches the ear of an observer directly from the source, and also after reflecting off a sound-reflecting surface. This phenomenon is called repetition pitch, because the addition of a true repetition of the original sound to itself is the basic prerequisite.
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Answer: when sound reaches the ear of an observer directly from the source, and also after reflecting off a sound-reflecting surface


Extract the answer to the question from the following context. Question: Wolves are not a type of? Context: The elimination of wolves from Yellowstone National Park had profound impacts on the trophic pyramid. Without predation, herbivores began to over-graze many woody browse species, affecting the area's plant populations. In addition, wolves often kept animals from grazing in riparian areas, which protected beavers from having their food sources encroached upon. The removal of wolves had a direct effect on beaver populations, as their habitat became territory for grazing. Furthermore, predation keeps hydrological features such as creeks and streams in normal working order. Increased browsing on willows and conifers along Blacktail Creek due to a lack of predation caused channel incision because they helped slow the water down and hold the soil in place.
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Answer: herbivores


Extract the answer to the question from the following context. Question: Who was given permission to use Bermudan air bases during World War 2? Context: In May 1940, the US requested base rights in Bermuda from the United Kingdom, but British Prime Minister Winston Churchill was initially unwilling to accede to the American request without getting something in return. In September 1940, as part of the Destroyers for Bases Agreement, the UK granted the US base rights in Bermuda. Bermuda and Newfoundland were not originally included in the agreement, but both were added to it, with no war material received by the UK in exchange. One of the terms of the agreement was that the airfield the US Army built would be used jointly by the US and the UK (which it was for the duration of the war, with RAF Transport Command relocating there from Darrell's Island in 1943).
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Answer:
US