How much more fuel does driving at 70mph use compared to 50mph?

Answer: C — 30 percent more fuel

Driving at higher speeds requires more energy and therefore more fuel to maintain that speed. The difference in fuel usage between 50mph and 70mph is not constant and may vary depending on the vehicle, but on average, driving at 70mph will use approximately 30% more fuel than driving at 50mph. Thus, options A, B, and D are incorrect as they underestimate the fuel usage difference between the two speeds.