Final answer:
To save fuel and get more miles per gallon, maintain a constant speed, use cruise control, avoid rapid acceleration and hard braking, and keep tires properly inflated. Over time, cars have become more fuel efficient, and choosing more sustainable transportation methods is beneficial for the environment.
Step-by-step explanation:
All of the statements provided are true and contribute to achieving better miles per gallon (MPG) and fuel efficiency. However, if I were to choose the most directly related statement to fuel efficiency, it would be:
4) Keeping tires properly inflated can improve fuel economy.
Maintaining proper tire pressure is crucial for better fuel economy. Underinflated tires increase rolling resistance, causing the engine to work harder and burn more fuel. By keeping tires properly inflated to the manufacturer's recommended pressure levels, you reduce this resistance, thus improving fuel efficiency.
Nevertheless, the other statements also play significant roles in enhancing fuel efficiency:
1) Driving at a constant speed on the highway can improve fuel efficiency because it minimizes the need for frequent acceleration and deceleration, which consumes more fuel.
2) Using cruise control can help maintain a consistent speed, which, similar to driving at a constant speed, can enhance fuel efficiency by avoiding unnecessary speed fluctuations.
3) Avoiding rapid acceleration and hard braking also contributes to better fuel efficiency by using fuel more efficiently and minimizing unnecessary energy loss through sudden stops and starts.