Final answer:
Reduced air density at high altitude leads to a decrease in the fuel-air mixture due to less oxygen being available for combustion, which results in reduced engine power.
Step-by-step explanation:
The reduced air density at high altitude has a significant effect on carburetion, which results in a reduction of engine power. This is because the air is thinner at higher elevations, which means less oxygen is available for combustion. Since engines require a specific ratio of fuel to air to operate efficiently, the lower oxygen levels lead to a leaner mixture because the proportion of air to fuel increases. Consequently, this lean mixture has less fuel relative to the amount of air than at sea level, which can cause the engine to produce less power.
Therefore, the correct answer to how the reduced air density at high altitude affects carburetion, resulting in the reduction of engine power is by:
- B) Decreasing the fuel-air mixture.