Final answer:
Turning onto a gravel road primarily affects driving conditions due to the loose surface that can challenge a vehicle's traction and potentially cause more wear and tear.
Step-by-step explanation:
If a suspect turns onto a gravel road, that primarily affects C. Driving Conditions. Gravel roads tend to be less stable and more slippery than paved roads. This can result in a loose surface for the tires to grip on, making it more challenging to maintain control of a vehicle, especially at higher speeds or during sudden maneuvers. Additionally, gravel can cause more wear and tear on a vehicle over time compared to asphalt or concrete roads due to the uneven surface and potential for rocks and debris to kick up.