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The logical format of an audio CD (officially Compact Disc Digital Audio or CD-DA) is described in a document produced in 1980 by the format's joint creators, Sony and Philips. The document is known colloquially as the Red Book CD-DA after the colour of its cover. The format is a two-channel 16-bit PCM encoding at a 44.1 kHz sampling rate per channel. Four-channel sound was to be an allowable option within the Red Book format, but has never been implemented. Monaural audio has no existing standard on a Red Book CD; thus, mono source material is usually presented as two identical channels in a standard Red Book stereo track (i.e., mirrored mono); an MP3 CD, however, can have audio file formats with mono sound.
When was four-channel sound implemented?
A: unanswerable

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The monogram theme was developed into an Art Deco-style badge on which the letters A and C framed a football rather than the letter F, the whole set within a hexagonal border. This early example of a corporate logo, introduced as part of Herbert Chapman's rebranding of the club in the 1930s, was used not only on Cup Final shirts but as a design feature throughout Highbury Stadium, including above the main entrance and inlaid in the floors. From 1967, a white cannon was regularly worn on the shirts, until replaced by the club crest, sometimes with the addition of the nickname "The Gunners", in the 1990s.
In what art style is the white cannon drawn?
A: unanswerable

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Bottom Up Testing is an approach to integrated testing where the lowest level components (modules, procedures, and functions) are tested first, then integrated and used to facilitate the testing of higher level components. After the integration testing of lower level integrated modules, the next level of modules will be formed and can be used for integration testing. The process is repeated until the components at the top of the hierarchy are tested. This approach is helpful only when all or most of the modules of the same development level are ready.[citation needed] This method also helps to determine the levels of software developed and makes it easier to report testing progress in the form of a percentage.[citation needed]
This approach only works when half of the modules of the same what are ready?
A: unanswerable

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During the Western Schism, many cardinals were created by the contending popes. Beginning with the reign of Pope Martin V, cardinals were created without publishing their names until later, termed creati et reservati in pectore.
What did Pope Pious V begin using?
A:
unanswerable