Which of the following best describes the role of gravity when you park your car on an incline?

Gravity plays a crucial role when parking a vehicle on an incline. When you park on an incline, gravity exerts a force that pulls the vehicle downward, which can cause it to roll if it's not properly secured. This is why it's essential to engage the parking brake and ensure that the vehicle is in gear (or in the "Park" position if it's an automatic transmission) when parked on an uphill or downhill slope. This preventive measure counters the gravitational force that could otherwise lead the vehicle to roll downhill.

The other options do not accurately reflect the influence of gravity in this scenario. For example, gravity does not maintain the vehicle's position; it actually works against it. Additionally, it is incorrect to say that gravity has no effect, as the force of gravity is always acting on the vehicle. Finally, gravity cannot cause the vehicle to roll uphill; rather, it consistently pulls objects downward unless counteracted by another force, such as friction or an incline.