What decreases as speed increases?

Answer: C — Visual acuity, field of vision, and depth perception

As speed increases, the visual demands on a driver also increase, resulting in decreased visual acuity, field of vision, and depth perception. This is due to the limited time available to process visual information and the increased distraction from high-speed movement. While engine noise may also increase at higher speeds, it is not the primary factor that decreases. Similarly, while the need for concentration may also increase, this is not the main effect of speed on the visual system. Fuel efficiency may decrease slightly at higher speeds due to increased aerodynamic resistance, but this effect is minimal compared to the impact on visual functions.