Answer: a. the car had been previously counted in the GDP of the year it was built.
Explanation: Though both used and new cars are sold in the U.S. by car dealers, the sale of used cars does not count because the car had been previously counted in the GDP of the year it was built. The Gross Domestic Product (GDP) which is defined as a measure of the economic production of a country in financial terms over a specific time period (usually a year), sums the dollar value of what has been produced in the economy over the year, not what was actually sold. In simpler terms, they were produced in a previous year and are part of that year's GDP.