Please answer this: Extract the answer to the question from the following context. Question: What are AAC, WMA Pro and Vorbis more effective than? Context: There are also open compression formats like Opus and Vorbis that are available free of charge and without any known patent restrictions. Some of the newer audio compression formats, such as AAC, WMA Pro and Vorbis, are free of some limitations inherent to the MP3 format that cannot be overcome by any MP3 encoder.
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Answer: any MP3 encoder

Please answer this: Extract the answer to the question from the following context. Question: Who retaliated? Context: The Russian Revolution is the series of revolutions in Russia in 1917, which destroyed the Tsarist autocracy and led to the creation of the Soviet Union. Following the abdication of Nicholas II of Russia, the Russian Provisional Government was established. In October 1917, a red faction revolution occurred in which the Red Guard, armed groups of workers and deserting soldiers directed by the Bolshevik Party, seized control of Saint Petersburg (then known as Petrograd) and began an immediate armed takeover of cities and villages throughout the former Russian Empire.
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Answer: Red Guard

Please answer this: Extract the answer to the question from the following context. Question: What is Metrorail? Context: Miami's heavy-rail rapid transit system, Metrorail, is an elevated system comprising two lines and 23 stations on a 24.4-mile (39.3 km)-long line. Metrorail connects the urban western suburbs of Hialeah, Medley, and inner-city Miami with suburban The Roads, Coconut Grove, Coral Gables, South Miami and urban Kendall via the central business districts of Miami International Airport, the Civic Center, and Downtown. A free, elevated people mover, Metromover, operates 21 stations on three different lines in greater Downtown Miami, with a station at roughly every two blocks of Downtown and Brickell. Several expansion projects are being funded by a transit development sales tax surcharge throughout Miami-Dade County.
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Answer:
Miami's heavy-rail rapid transit system