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Which of the following is one of the two important sources of the significant drop in U.S. emissions of CO2 between 2007 and 20127 O U.S. gasoline prices rose considerably over the period. The Great Recession of 2009-13 slowed economic growth, which slowed CO2 emissions, O U.S. manufacturing activity grew over the period despite slower economic growth. The high price of natural gas slowed the substitution of natural gas for coal used in generating electricity. Counterproductive economic behavior could be more prevalent in developing countries because of @ a shortage of strong institutions. O government interference in economic affairs. O overspending on defense. insufficient social spending