Which tax was the highest in 2015?

Answer: A — Federal diesel tax

The federal diesel tax was the highest in 2015 because it is specifically designed to fund the Highway Trust Fund, which supports the construction and maintenance of the nation’s highways and transit systems. The federal diesel tax is set at 24.4 cents per gallon, which is higher than many state gasoline taxes. On the other hand, while state gasoline taxes vary, they typically do not reach the same levels as federal taxes on diesel fuel. Sales tax varies widely across states and is imposed based on the sale of goods and services, making it less relevant when considering transportation-specific taxes. The fuel efficiency tax is not a standard tax levied on fuels but rather relates to vehicle efficiency regulations, which do not directly compare as a tax measure. Therefore, the federal diesel tax stands out as the highest in 2015 among these options.