The widely accepted big bang theory holds that the universe began in an explosive instant ten to twenty billion years ago and has been expanding ever since.
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Athat the universe began in an explosive instant ten to twenty billion years ago and has been expanding
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Bthat the universe had begun in an explosive instant ten to twenty billion years ago and had been expanding
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Cthat the beginning of the universe was an explosive instant ten to twenty billion years ago that has expanded
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Dthe beginning of the universe to have been an explosive instant ten to twenty billion years ago that is expanding
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Ethe universe to have begun in an explosive instant ten to twenty billion years ago and has been expanding
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