Answer:
If I had to choose one vehicle to make changes to, I would choose a truck. To make changes to a truck, I would improve the fuel efficiency by adding more aerodynamic features such as a spoiler, grille shutters, and side skirts. I would also replace the existing engine with a more efficient one and replace the tires with ones that have a lower rolling resistance. Additionally, I would install a solar panel on the roof to charge the battery and reduce the amount of energy consumed by the truck. Finally, I would add a start-stop system to the vehicle, so that it automatically shuts off when the truck is idling.