Dear beloved readers, welcome to our website! We hope your visit here brings you valuable insights and meaningful inspiration. Thank you for taking the time to stop by and explore the content we've prepared for you.
------------------------------------------------ The mode of transportation which has the highest fuel economy as measured by the number of ton-miles per gallon of fuel is:

(a) Truck
(b) Rail
(c) Air
(d) Water

Water transportation (d) is the most fuel-efficient mode of transport on a ton-mile per gallon basis, significantly outperforming trucks, rail, and air transport due to its capacity to carry a massive volume of cargo.

Explanation:

The mode of transportation with the highest fuel economy as measured by number of ton-miles per gallon of fuel is water (d) transport. This means that when considering the energy requirements for various modes of transportation, ships are about four times more efficient per ton, able to carry 5,000 times more cargo compared to other modes. Despite trucks having a better kilowatt-hours per kilometer (kWh/km) measure than ships, the sheer volume of cargo ships can carry makes them significantly more efficient on a per-ton basis. Air freight, on the other hand, is 100 times more energetically costly than transporting by ship, making it the least efficient in terms of fuel economy for cargo transportation.