input: Please answer the following: Extract the answer to the question from the following context. Question: A music piece intended to be played with only vocal singers, and is not accompanied with any musical instrument is? Context: The Swingle Singers used nonsense words to sound like instruments, but have been known to produce non-verbal versions of musical instruments. Like the other groups, examples of their music can be found on YouTube. Beatboxing, more accurately known as vocal percussion, is a technique used in a cappella music popularized by the hip-hop community, where rap is often performed a cappella also. The advent of vocal percussion added new dimensions to the a cappella genre and has become very prevalent in modern arrangements. Petra Haden used a four-track recorder to produce an a cappella version of The Who Sell Out including the instruments and fake advertisements on her album Petra Haden Sings: The Who Sell Out in 2005. Haden has also released a cappella versions of Journey's "Don't Stop Believin'", The Beach Boys' "God Only Knows" and Michael Jackson's "Thriller". In 2009, Toyota commissioned Haden to perform three songs for television commercials for the third-generation Toyota Prius, including an a cappella version of The Bellamy Brothers' 1970s song "Let Your Love Flow".[citation needed]
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output: a cappella

input: Please answer the following: Extract the answer to the question from the following context. Question: What kind of album is ZZ Top's Eliminator? Context: Established bands made something of a comeback in the mid-1980s. After an 8-year separation, Deep Purple returned with the classic Machine Head line-up to produce Perfect Strangers (1984), which reached number five in the UK, hit the top five in five other countries, and was a platinum-seller in the US. After somewhat slower sales of its fourth album, Fair Warning, Van Halen rebounded with the Top 3 album Diver Down in 1982, then reached their commercial pinnacle with 1984. It reached number two on the Billboard album chart and provided the track "Jump", which reached number one on the singles chart and remained there for several weeks. Heart, after floundering during the first half of the decade, made a comeback with their eponymous ninth studio album which hit number one and contained four Top 10 singles including their first number one hit. The new medium of video channels was used with considerable success by bands formed in previous decades. Among the first were ZZ Top, who mixed hard blues rock with new wave music to produce a series of highly successful singles, beginning with "Gimme All Your Lovin'" (1983), which helped their albums Eliminator (1983) and Afterburner (1985) achieve diamond and multi-platinum status respectively. Others found renewed success in the singles charts with power ballads, including REO Speedwagon with "Keep on Loving You" (1980) and "Can't Fight This Feeling" (1984), Journey with "Don't Stop Believin'" (1981) and "Open Arms" (1982), Foreigner's "I Want to Know What Love Is", Scorpions' "Still Loving You" (both from 1984), Heart's "What About Love" (1985) and "These Dreams" (1986), and Boston's "Amanda" (1986).
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output: diamond

input: Please answer the following: Extract the answer to the question from the following context. Question: What suggests that birds have a slightly complex brain? Context: The timing of migration seems to be controlled primarily by changes in day length. Migrating birds navigate using celestial cues from the sun and stars, the earth's magnetic field, and probably also mental maps.
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output: mental maps

input: Please answer the following: Extract the answer to the question from the following context. Question: This city holds the number one slot in the book of firsts for its establishment of a variety of institutions including medical schools? Context: The area's many universities and colleges make Philadelphia a top international study destination, as the city has evolved into an educational and economic hub. With a gross domestic product of $388 billion, Philadelphia ranks ninth among world cities and fourth in the nation. Philadelphia is the center of economic activity in Pennsylvania and is home to seven Fortune 1000 companies. The Philadelphia skyline is growing, with several nationally prominent skyscrapers. The city is known for its arts, culture, and history, attracting over 39 million domestic tourists in 2013. Philadelphia has more outdoor sculptures and murals than any other American city, and Fairmount Park is the largest landscaped urban park in the world. The 67 National Historic Landmarks in the city helped account for the $10 billion generated by tourism. Philadelphia is the birthplace of the United States Marine Corps, and is also the home of many U.S. firsts, including the first library (1731), first hospital (1751) and medical school (1765), first Capitol (1777), first stock exchange (1790), first zoo (1874), and first business school (1881). Philadelphia is the only World Heritage City in the United States.
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output:
Philadelphia