Final answer:
The closest option to the percentage of global greenhouse gas emissions caused by the transportation sector, based on the information provided and U.S. data, is 20%.
Step-by-step explanation:
The transportation sector is responsible for a significant portion of global greenhouse gas emissions due to the burning of fossil fuels for road, rail, air, and marine transportation. Data from the U.S. Environmental Protection Agency suggests that in the United States in 2018, more than one-quarter, specifically 28.2 percent, of emissions were the result of consuming fossil fuels for transportation. Over half of these emissions emanated from passenger cars, light-duty trucks, sport utility vehicles, and minivans.
Given this information, several mitigation priorities are suggested, including using fuels that emit less carbon, improving fuel efficiency, and decreasing travel necessity through better urban planning, telecommuting, and enhancing biking and pedestrian infrastructure. However, the provided options for the percentage of global greenhouse gas emissions specifically caused by the transportation sector do not perfectly match the stated data for the U.S. but considering the numbers involved, the closest option would be (b) 20%.