World population passed the 1 billion mark in ____ and the 3 billion mark in _____.

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     1860,1975
      1830,1930
      1930,1987
      1830,1960
asked Jun 25, 2012 in Environmental Science by anonymous
    

1 Answer

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1830,1960
answered Jun 26, 2012 by Geodude ~Top Expert~ (9,680 points)

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