The answer is: As close to the antecedent as possible<span>
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Answer:
The combined length of the Missouri-Mississippi river system, from headwaters [of the Missouri river] in southern Montana, to the mouth of the Mississippi near New Orleans [Louisiana], is aproximately 6,267 km (3,895 mi), making it the world's fourth longest river system, after the Nile, the Amazon, and the Yangtze.
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