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Energy conservation


A chronicle of new vehicle fuel economies was published by the U.S. Environmental Protection Agency in the 2020 Automotive Trends Report.
A line graph has an x axis titled Model Year that spans from nineteen seventy five to two thousand and twenty five. The y axis is titled Real World Fuel Economy and ranges from about twelve to twenty six miles per gallon. From nineteen seventy five to about nineteen eighty two, the line rapidly increases, from approximately thirteen to twenty one miles per gallon. The line reaches twenty two miles per gallon around nineteen eighty eight. From this time to two thousand and five, the line slowly decreases, reaching nineteen miles per gallon. After this, there is a steady increase to about twenty five miles per gallon in two thousand and nineteen, where the line ends.
Which of the following factors is most likely to have triggered the change in fuel economy that began in 2004?
Choose 1 answer: